This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A133047 #13 Dec 15 2014 23:43:23 %S A133047 1,7,49,216,805,2733,9105,28123,85340,255800,768155,2265062,6588759, %T A133047 18667410,51448497,137051636,353575584,878804335,2113497469, %U A133047 4908984819,11049271004,24062242901,50742319631 %N A133047 Starting from the standard 12 against 12 starting position in checkers, the sequence gives the number of distinct positions that can arise after n moves. %C A133047 These numbers are generally smaller than those in A133046 because one line of play can transpose into another. %Y A133047 Cf. A133046, A055213. %K A133047 nonn,nice %O A133047 0,2 %A A133047 Jonathan Schaeffer (jonathan(AT)cs.ualberta.ca), Dec 27 2007 %E A133047 a(16)-a(22) computed by _Paul Byrne_, Sep 2012