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 A307993 #6 May 09 2019 15:00:03
%S A307993 1,1,1,1,2,2,3,3,5,4,6,7,8,7,13,9,12,17,15,13,27,16,22,32,24,23,48,27,
%T A307993 33,55,40,34,79,41,49,87,55,55,122,56,72,132,81,73,174,82,98,196,106,
%U A307993 99,253,110,131,267,144,132,342,153,175,359,188,176,459,189,218,496,238,229,602
%N A307993 G.f. A(x) satisfies: A(x) = x + x^2 + x^3 * (1 + A(x) + A(x^2) + A(x^3) + ...).
%C A307993 Shifts left 3 places under inverse Moebius transform.
%F A307993 G.f.: x + x^2 + x^3 * (1 + Sum_{n>=1} a(n)*x^n/(1 - x^n)).
%F A307993 a(1) = a(2) = a(3) = 1; a(n+3) = Sum_{d|n} a(d).
%t A307993 terms = 69; A[_] = 0; Do[A[x_] = x + x^2 + x^3 (1 + Sum[A[x^k], {k, 1, terms}]) + O[x]^(terms + 1) // Normal, terms + 1]; Rest[CoefficientList[A[x], x]]
%t A307993 a[n_] := a[n] = SeriesCoefficient[x + x^2 + x^3 (1 + Sum[a[k] x^k/(1 - x^k), {k, 1, n - 1}]), {x, 0, n}]; Table[a[n], {n, 1, 69}]
%t A307993 a[n_] := a[n] = Sum[a[d], {d, Divisors[n - 3]}]; a[1] = a[2] = a[3] = 1; Table[a[n], {n, 1, 69}]
%Y A307993 Cf. A003238, A007439, A307994, A307995.
%K A307993 nonn
%O A307993 1,5
%A A307993 _Ilya Gutkovskiy_, May 09 2019