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 A345139 #4 Jun 09 2021 11:14:36
%S A345139 1,2,3,6,7,13,14,23,27,37,38,63,64,81,92,124,125,171,172,225,243,284,
%T A345139 285,396,404,471,502,606,607,762,763,919,961,1089,1111,1397,1398,1573,
%U A345139 1641,1942,1943,2300,2301,2632,2762,3050,3051,3682,3697,4148,4277,4821,4822,5541,5587
%N A345139 a(1) = 1; a(n) = a(n-1) + Sum_{d|n, d < n} a(d).
%F A345139 G.f. A(x) satisfies: A(x) = (1/(1 - x)) * (x + A(x^2) + A(x^3) + A(x^4) + ...).
%t A345139 a[1] = 1; a[n_] := a[n] = a[n - 1] + Sum[If[d < n, a[d], 0], {d, Divisors[n]}]; Table[a[n], {n, 1, 55}]
%t A345139 nmax = 55; A[_] = 0; Do[A[x_] = (1/(1 - x)) (x + Sum[A[x^k], {k, 2, nmax}]) + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x] // Rest
%Y A345139 Cf. A074206, A084978, A330575.
%K A345139 nonn
%O A345139 1,2
%A A345139 _Ilya Gutkovskiy_, Jun 09 2021