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 A287880 #3 Jun 18 2017 14:25:11 %S A287880 1,3,7,25,61,219,547,1937,4921,17203,44287,153193,398581,1366795, %T A287880 3587227,12211873,32285041,109226595,290565367,977773625,2615088301, %U A287880 8758657339,23535794707,78500250929,211822152361,703877909907,1906399371247,6313707508105,17157594341221,56650974993259 %N A287880 Row sums of triangle in A287879, divided by 2. %Y A287880 Cf. A287879. %K A287880 nonn %O A287880 1,2 %A A287880 _N. J. A. Sloane_, Jun 18 2017