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 A309045 #6 Jul 09 2019 11:14:57
%S A309045 1,1,1,3,2,2,5,3,3,11,8,8,19,11,11,25,14,14,41,27,27,59,32,32,70,38,
%T A309045 38,110,72,72,158,86,86,190,104,104,289,185,185,395,210,210,455,245,
%U A309045 245,645,400,400,829,429,429,915,486,486,1269,783,783,1623,840,840,1800,960,960,2472
%N A309045 Expansion of Product_{k>=0} (1 + x^(3^k) + x^(2*3^k) + x^(3^(k+1)))^(2^k).
%C A309045 The trisection equals the self-convolution of this sequence.
%F A309045 G.f.: Product_{k>=0} ((1 - x^(4*3^k))/(1 - x^(3^k)))^(2^k).
%F A309045 G.f. A(x) satisfies: A(x) = (1 + x + x^2 + x^3) * A(x^3)^2.
%t A309045 nmax = 63; CoefficientList[Series[Product[(1 + x^(3^k) + x^(2 3^k) + x^(3^(k + 1)))^(2^k), {k, 0, Floor[Log[3, nmax]] + 1}], {x, 0, nmax}], x]
%t A309045 nmax = 63; A[_] = 1; Do[A[x_] = (1 + x + x^2 + x^3) A[x^3]^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%Y A309045 Cf. A054390, A237651, A309046.
%K A309045 nonn
%O A309045 0,4
%A A309045 _Ilya Gutkovskiy_, Jul 09 2019