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 A287960 #10 Feb 16 2025 08:33:47
%S A287960 2,5,8,11,14,20,23,29,32,35,38,41,47,50,56,62,65,68,74,77,83,86,89,92,
%T A287960 95,104,110,113,116,119,128,131,137,140,146,149,155,167,170,173,176,
%U A287960 182,185,194,197,200,203,209,212,218,221,230,236,239,245,251,254,263,266,272,275,278,281,284,293,299
%N A287960 Numbers that are the sum of two centered triangular numbers (A005448).
%H A287960 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CenteredTriangularNumber.html">Centered Triangular Number</a>
%H A287960 <a href="/index/Ce#CENTRALCUBE">Index entries for sequences related to centered polygonal numbers</a>
%F A287960 8*a(n) = 10+3*A097269(n). - _R. J. Mathar_, Jul 26 2017
%t A287960 nmax = 300; f[x_] := Sum[x^(3 k (k - 1)/2 + 1), {k, 1, 20}]^2; Exponent[#, x] & /@ List @@ Normal[Series[f[x], {x, 0, nmax}]]
%Y A287960 Cf. A005448, A020756, A051533, A102795, A286636.
%K A287960 nonn
%O A287960 1,1
%A A287960 _Ilya Gutkovskiy_, Jun 03 2017