Re:The On-Line Encyclopedia of Integer Sequences
by Terr_ on Tuesday July 21, 2015 @12:55AM
(#9920628)
Well, the last time it helped me was as a "reverse lookup" for math knowledge I never got the "right" way through education.
For example, one of the Google-Foobar puzzles involves how many ways you can order a line of different-height elements so that only a certain number are "visible" if you stood at one end of the line or the other.
First I tried to figure out how I would solve it for small numbers by hand, creating a spreadsheet of inputs. At one point, I got a grid of numbers where the "simpler" rows/columns had a sequence like 1, 1, 1, 2, 3, 1, 6, 11, 6, which, through random googling and OEIS turned out to be "Unsigned Stirling numbers of the first kind"
Alas, I'm still no math-major... the comments in my solution contain: "I'm extremely proud of this boiled-down end-result... except that I'm not sure I can fully explain why it works."
For example, one of the Google-Foobar puzzles involves how many ways you can order a line of different-height elements so that only a certain number are "visible" if you stood at one end of the line or the other.
First I tried to figure out how I would solve it for small numbers by hand, creating a spreadsheet of inputs. At one point, I got a grid of numbers where the "simpler" rows/columns had a sequence like 1, 1, 1, 2, 3, 1, 6, 11, 6, which, through random googling and OEIS turned out to be "Unsigned Stirling numbers of the first kind"
http://oeis.org/A008275 https://en.wikipedia.org/wiki/Stirling_numbers_of_the_first_...
Alas, I'm still no math-major... the comments in my solution contain: "I'm extremely proud of this boiled-down end-result... except that I'm not sure I can fully explain why it works."