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 A209980 #5 Mar 30 2012 18:58:16 %S A209980 0,0,1,3,9,15,25,35,49,59,81,99,113,135,169,183,213,243,277,311,341, %T A209980 363,421,463,493,531,601,635,681,735,781,839,901,939,1033,1079,1125, %U A209980 1195,1301,1347,1409,1487,1557,1639,1717,1763,1893,1983,2045,2127 %N A209980 (A197168)/2. %C A209980 See A210000 for a guide to related sequences. %t A209980 (See the Mathematica section at A209978.) %Y A209980 Cf. A210000. %K A209980 nonn %O A209980 0,4 %A A209980 _Clark Kimberling_, Mar 16 2012