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 A361515 #11 Apr 09 2023 02:01:31
%S A361515 1,3,5,7,9,12,14,18,25,28,21,42,32,80,39,71,47,77,53,100,59,115,88,67,
%T A361515 147,120,106,128,94,154,187,142,178,161,134,170,226,205,246,327,287,
%U A361515 217,313,196,236,334,506,348,266,302,256,359,406,374,481,416,471,383,431,280
%N A361515 a(n) = index of first appearance of n in A361511, or -1 if n never appears.
%C A361515 Conjecture: This is a permutation of the positive integers.
%H A361515 Michael De Vlieger, <a href="/A361515/b361515.txt">Table of n, a(n) for n = 1..17878</a> (All terms that appear in a(n) for n = 1..2^24)
%t A361515 nn = 1000; c[_] = False; q[_] = 0; f[n_] := DivisorSigma[0, n]; a[1] = m = 1; Do[(If[c[#], a[n] = # + f[a[m]] ; m++, a[n] = f[#] ]; c[#] = True; If[q[#] == 0, q[#] = n - 1]) &[a[n - 1]], {n, 2, nn}]; TakeWhile[Array[q, nn], # > 0 &] (* _Michael De Vlieger_, Apr 08 2023 *)
%Y A361515 Cf. A361511-A361514.
%K A361515 nonn
%O A361515 1,2
%A A361515 _N. J. A. Sloane_, Apr 08 2023