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 A131906 #5 Apr 03 2015 03:47:59
%S A131906 6,24,30,40,66,78,102,120,114,120,136,138,150,168,174,186,186,230,222,
%T A131906 280,264,246,258,280,318,330,354,360,366,430,408,390,402,408,456,426,
%U A131906 438,440,474,498,510,552,520,534,600,645,570,582,606,618,642,696,654,680
%N A131906 Smallest positive integer k with the same sum of squares of divisors as the n-th integer for which such a k exists.
%F A131906 a(n)=min(k>0, k has the same sum of squares of divisors as A131905(n))
%e A131906 a(5)=66 because A131905(5)=77 and the sum of the squares of the divisors of 77 is 1+49+121+5929=6100 and the sum of the squares of the divisors of 66 is 1+4+9+36+121+484+1089+4356=6100 and there is no smaller positive integer with this squaresum of its divisors
%t A131906 Clear[tmp]; Last@Transpose[ Function[n, (If[Head[ #1] === tmp, #1 = n; Unevaluated[Sequence[]], {n, #1}] & )[tmp[DivisorSigma[2, n]]]] /@ Range[500]]
%o A131906 (PARI) lista(nn) = {for (n=1, nn, my(sn = sigma(n,2)); for (k=1, n-1, if (sigma(k, 2) == sn, print1(k, ", "); break);););} \\ _Michel Marcus_, Apr 03 2015
%Y A131906 Cf. A069822, A131902-A131908.
%K A131906 easy,nonn
%O A131906 1,1
%A A131906 Peter Pein (petsie(AT)dordos.net), Jul 26 2007
%E A131906 More terms from _Michel Marcus_, Apr 03 2015