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Vadim asked the following brain teaser:

 How many squares are there on a chess board?

Yes, it’s a trick question but the solutions were better than the question or the answer.

Ik came up with a solution in Emacs Lisp:

(let ((f (lambda (n) (cond ((= n 1) 1) (t (+ (* n n) (f (1- n)))))))) (f 8))

Bill came up with one using DC, the RPN desk calculator, that just floored us and had us running to read the man pages:

echo "8sc0sr[q]sb[lc0lc=bdlr+srlc1-sclax]salaxlrpq" | dc

Look closely at that one and think through it. Clever. Clever. The underlying simplicity is brilliant.

Based on Bill’s and Ik’s I cobbled together an obfuscated answer in Perl (save to a file, shell quoting mungs it):

#!perl -e $/=$@;$;=8;sub'f{$/+=$;--*2;$;}sub'g{&f&&&g}g;print$/$^L

Like theirs, it uses recursion but I try to hide what’s going because I am not clever.

I was so busy this weekend but, unless you’re interested in my groceries or cleaning the apartment, it’s a short list of events:

• Saw Elvis Costello at Central Park SummerStage on Friday. Maria’s coworker’s daughter is the organizer and got us VIP passes, putting us on bleachers directly in front of the stage. This is so much better than general admission it might be enough to convince Maria to go to more concerts. Rain hit during the opening act, Chris Robinson formerly of the Black Crows, but we had umbrellas and several of us crowded under them. Elvis Costello was in very good voice that evening and did three encores. His touring band, the Impostors, were in equally good form and everything sounded great. The graying of the crowd was as interesting as anything else and it’s sort of weird to see folks rocking out while their nine and ten year old kids clap and sway next to them.
• I skipped the gym on Friday because I knew I would make up for it the next day. I cleared land with my friend Charlie in Dutchess county on Saturday. I’m also glad I’ve been going to the gym regularly because I haven’t done much real labor in a few years and I didn’t want to be sore after one day (I wasn’t, except for my knee) or useless halfway through the day. The place used to be a farm pasture and the two and a half acres intended for the house had completely grown over with maple, poplar, pin oak and a few ash. Amazing how tall these grow in twenty years. In the previous few weeks he had done a huge amount of work- there must have been ten or eleven cords of wood piled near the edges- getting the lot ready for construction and there was more to do. We felled trees, cleared brush, picked up trash and debris and when I wasn’t working, I raced around on his new Polaris ATV laughing like a fool. It’s a work horse 2003 leftover but in high gear I got up to 45 mph before scaring myself and backing off the throttle, it will jump stumps and deep ruts at speed (hence the sore knee) and it will do a quick wheelie if you thumb hard at the throttle from a stop. A few days before Kelly brought a backhoe loader (I was looking forward to that). We would have pulled stumps but it had blown a hydraulic seal on one of the stabilizers the previous afternoon and we couldn’t use it without showering oil everywhere. Darn. Managed not to kill or maim myself or anyone else with the pruning hook, chainsaws, atv or industrial chipper. The chipper, which we spent an hour dismantling and clearing after a small green sapling- along with the cotton rags and what looked like a roll of duct tape some previous user had chucked into it- wrapped up the disk and stalled it. I managed not to get stung or bitten by anything thanks to the usual field clothes of long sleeves, long socks, boots, tucked in jeans and gloves but probably due more to lots and lots of DEET. If my future offspring are dullards, this will be why. I also didn’t get on me any of the poison ivy that seemed to grow everywhere.

Interesting and amusing article in Slate on Gore-Tex in rain gear. It’s a more entertaining read than Consumer Reports even if most of it is subjective.

I’ll be on vacation later this summer and will want to get to my home systems to check email, upload pictures and the like but I don’t want to drag my laptop around with me (which also means carrying around an international power converter suitable for extended use and they’re bulky). My idea was to use whatever unsecured or public access terminal I can find and SSH. Fine, except that I already don’t trust the host so I don’t want to put my public key on it meaning I have to use password authentication. But using SSH this way means typing my reusable password and I already don’t trust the host I’m logging in from. Solution? Use a One-Time Password (otp) authentication system. Read the man pages and I had it set up in about sixty seconds on my *BSD systems. Works great! I can print out a list of single use passwords and keep it in my wallet or load an OTP client on my palm pilot and generate them on the fly. Cool. My Linux host, however, is a different story. Seems that PAM, the pluggable authentication module system, SSH and challenge/response authentication don’t work together and haven’t since at least mid-2002. First, Privilege Separation doesn’t work if PAM is used. Annoying, since dropping root privs by the SSH daemon is a good idea. There is no generally working exploit (yet) against a patched non-PrivSep sshd but I’d rather not find out the hard way when it emerges. Second, you can only use one of challenge/response or password but not both unless you intend to use both together, i.e. you first authenticate with a otp and then with the reusable password. That sucks. I might use OTP with SSH to get to one of the OpenBSD hosts and put a public key to an account on the firewalled Linux box (and install keys to jump to the others, so I don’t expose passwords) but that stinks of creating a new security hole. I might just disable password authentication to the Linux box and only use OTP for the duration of my trip.

We had a short layover today returning from visiting friends. The Memphis, TN airport is badly served in terms of food. They pack four kiosk sized fast-food vendors into the space normally arranged for one and corporate branding ideals keep the sellers from posting menus and prices anywhere but at the counter, a position reached after already making your choice and waiting on interminable lines that impede moving between terminals. I’m not sure how this reinforces anyone’s remaining brand loyalty.

The airlines, as a cost cutting move, have not served meals on most economy flights (though you do get a whole can of soda, whohoo) for a while. Cleverly, they are test marketing the sale of a limited number of prepared meals for a good deal more, considering the quantity of food, than what is sold in the terminal. It’s a good idea but the execution is poor. This time not only do you not read the menu until your choices are constrained- you’re not going anywhere relative to your seat to buy food now- but you don’t even learn that your particular flight is offering these choices until you are already in the air. The only possible customer in this situation would be the impulse buyer. If it’s popular, and profitable, it will probably become a regular feature of domestic flights. Seems like a good idea. Commodity airfare looks like it has pushed the airlines into the same sales niche as movie theaters- the product is pretty much the same from anywhere and prices are highly constrained so you try to distinguish your brand and end up making it up at the concession stand.

Maria commented how nice an automat would be. That is a great idea. When I have thirty minutes to catch a connecting flight I don’t want to spend twenty of it on a line buying McKentuckyHut (we bought sandwiches from a regional chain, by the way, the decision almost entirely based upon the length of the line). In the space of one vendor you could put in the automat’s assembly of little doors. The food is loaded from behind and each item kept fresh and appropriately hot or cold. Like the Febo in the Netherlands (eating at the wall), the items should be inexpensive and tasty and proportioned in such a way that a single item is not quite enough to fill you up, encouraging you to buy two or more. For convenience, these automats should accept debit and credit cards as wall as cash and coins. Despite being "retro" I think it would work- people are comfortable buying from vending machines- and this would return airport food to where it belongs: just another commodity