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 A291089 #8 Sep 01 2017 23:50:29 %S A291089 1,4,20,104,556,3032,16778,93872,529684,3008864,17184188,98577712, %T A291089 567591142,3278348608,18986482250,110217131168,641125473092, %U A291089 3736134109936,21807240851480,127469052615104,746057665449076,4371699398312704,25644387465768860 %N A291089 a(n) = A026520(2n+1). %H A291089 Lars Blomberg, <a href="/A291089/b291089.txt">Table of n, a(n) for n = 0..500</a> %Y A291089 Cf. A026520, A291088. %K A291089 nonn %O A291089 0,2 %A A291089 _N. J. A. Sloane_, Aug 19 2017 %E A291089 a(15)-a(22) from _Lars Blomberg_, Sep 01 2017