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 A121871 #10 Sep 30 2017 04:46:14 %S A121871 1,2,-2,11,-12,2,52,-70,20,-2,269,-392,150,-28,2,1414,-2186,1000,-262, %T A121871 36,-2 %N A121871 Triangle read by rows: see DeTemple et al. reference for definition. %H A121871 D. DeTemple and M. Hudelson, <a href="http://www.jstor.org/stable/2695523">Square-banded polygons and affine regularity</a>, Amer. Math. Monthly, 108 (No. 2, 2001), 100-114. %e A121871 Triangle begins: %e A121871 1 %e A121871 2 -2 %e A121871 11 -12 2 %e A121871 52 -70 20 -2 %e A121871 269 -392 150 -28 2 %Y A121871 Leading diagonal is A026933. %K A121871 sign,tabl,more %O A121871 1,2 %A A121871 _N. J. A. Sloane_, Sep 05 2006