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 A265137 #12 Dec 26 2015 18:39:01
%S A265137 471,531,601,616,786,871,906,991,1056,1126,1156,1186,1281,1296,1341,
%T A265137 1381,1446,1486,1551,1576,1602,1641,1656,1771,1806,1836,1896,1906,
%U A265137 1921,2031,2044,2061,2146,2226,2265,2281,2316,2356,2401,2421,2451,2486,2551,2646
%N A265137 Numbers that are the sum of two distinct nonzero triangular numbers in more than three ways.
%C A265137 If there exists any 3 X 3 magic square composed of triangular numbers, then its magic sum is a(n) + A000217(m) for some m and n.
%t A265137 r = 2646; lst = Table[0, {r}]; lim = Floor[Sqrt[8*r - 7]]; Do[num = (i^2 + i)/2 + (j^2 + j)/2; If[num <= r, lst[[num]]++], {i, lim}, {j, i - 1}]; Flatten@Position[lst, n_ /; n > 3]
%t A265137 Module[{nn=80,trnos},trnos=Accumulate[Range[nn]];Select[Sort[ Flatten[ Table[ PositionIndex[Counts[Total/@Subsets[trnos,{2}]]][i],{i,4,nn}]]], #<= Last[trnos]&]] (* The program uses the PositionIndex and Counts functions from Mathematica version 10 *) (* _Harvey P. Dale_, Dec 26 2015 *)
%Y A265137 Cf. A000217, A051533, A260647, A265140 (exactly one way), A262749 (more than one way), A265134 (exactly two ways), A265135 (more than two ways), A265136 (exactly three ways), A265138 (exactly four ways).
%K A265137 nonn
%O A265137 1,1
%A A265137 _Arkadiusz Wesolowski_, Dec 02 2015