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 A209989 #5 Mar 30 2012 18:58:16 %S A209989 0,0,13,29,91,123,171,219,315,363,459,539,667,763,907,971,1163,1291, %T A209989 1435,1579,1835,1931,2171,2347,2539,2699,2987,3131,3515,3739,3931, %U A209989 4171,4555,4715,5099,5291,5675,5963,6395,6587,6971 %N A209989 (A209988)/4. %C A209989 See A210000 for a guide to related sequences. %t A209989 (See the Mathematica section at A209981.) %Y A209989 Cf. A210000. %K A209989 nonn %O A209989 0,3 %A A209989 _Clark Kimberling_, Mar 17 2012