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 A255256 #17 Oct 26 2018 09:40:06 %S A255256 1,1,1,1,2,1,1,4,4,1,1,8,14,8,1,1,16,50,50,16,1,1,32,178,276,178,32,1, %T A255256 1,64,634,1498,1498,634,64,1,1,128,2258,8352,10980,8352,2258,128,1,1, %U A255256 256,8042,46730,85138,85138,46730,8042,256,1,1,512,28642,260204,655090,781712,655090,260204,28642,512,1 %N A255256 Number A(n,k) of 2-colorings of a k X n rectangle such that no nontrivial subsquare has monochromatic corners; square array A(n,k), n>=0, k>=0, read by antidiagonals. %H A255256 Alois P. Heinz, <a href="/A255256/b255256.txt">Antidiagonals n = 0..12</a> %e A255256 A(2,2) = 2^(2*2) - 2 = 14 because there are exactly two of sixteen 2-colorings of the 2 X 2 square resulting in nontrivial subsquares with monochromatic corners. %e A255256 Square array A(n,k) begins: %e A255256 1, 1, 1, 1, 1, 1, 1, ... %e A255256 1, 2, 4, 8, 16, 32, 64, ... %e A255256 1, 4, 14, 50, 178, 634, 2258, ... %e A255256 1, 8, 50, 276, 1498, 8352, 46730, ... %e A255256 1, 16, 178, 1498, 10980, 85138, 655090, ... %e A255256 1, 32, 634, 8352, 85138, 781712, 6965108, ... %e A255256 1, 64, 2258, 46730, 655090, 6965108, 58339148, ... %Y A255256 Columns (or rows) k=0-5 give: A000012, A000079, A055099, A133357, A255255, A255262. %Y A255256 Main diagonal gives A018803. %K A255256 nonn,tabl %O A255256 0,5 %A A255256 _Alois P. Heinz_, Feb 19 2015