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 A374626 #19 Jul 15 2024 10:23:08
%S A374626 1,3,9,30,90,270,819,2457,7371,22143,66429,199287,597951,1793853,
%T A374626 5381559,16144947,48434841,145304523,435914388,1307743164,3923229492,
%U A374626 11769690933,35309072799,105927218397,317781662562,953344987686,2860034963058,8580104911317
%N A374626 Expansion of Product_{k>=0} 1 / (1 - 3*x^(3^k)).
%F A374626 G.f. A(x) satisfies A(x) = A(x^3)/(1 - 3*x).
%F A374626 a(n) is divisible by 3 for n > 0.
%o A374626 (PARI) my(N=30, x='x+O('x^N)); Vec(1/prod(k=0, logint(N,3), 1-3*x^3^k))
%Y A374626 For generating functions Product_{k>=0} 1 / (1 - a*x^(b^k)) for the following values of (a,b) see: (1,2) A018819, (1,3) A062051, (2,2) A309728.
%Y A374626 Cf. A117940.
%K A374626 nonn
%O A374626 0,2
%A A374626 _Seiichi Manyama_, Jul 14 2024