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 A306158 #21 Apr 13 2025 07:24:11
%S A306158 4,10,20,70,204,690,2340,8230,29120,104958,381300,1398430,5162220,
%T A306158 19175130,71582716,268439590,1010580540,3817763040,14467258260,
%U A306158 54975633906,209430785460,799645010850,3059510616420,11728124726270,45035996273664,173215372864590
%N A306158 Inverse Weigh transform of 4^n.
%H A306158 Seiichi Manyama, <a href="/A306158/b306158.txt">Table of n, a(n) for n = 1..1000</a>
%H A306158 Christian G. Bower, <a href="https://oeis.org/transforms_pari.txt">PARI programs for transforms</a>, 2007.
%H A306158 N. J. A. Sloane, <a href="/transforms.txt">Maple programs for transforms</a>, 2001-2020.
%F A306158 Product_{k>=1} (1+x^k)^a(k) = 1/(1-4x).
%F A306158 a(n) = (1/n) * (4^n + Sum_{d<n and d|n} (-1)^(n/d) * d * a(d)).
%e A306158 (1+x)^4*(1+x^2)^10*(1+x^3)^20*(1+x^4)^70* ... = 1 + 4*x + 16*x^2 + 64*x^3 + 256*x^4 + ... .
%Y A306158 Inverse Weigh transform of b^n: A306156 (b=2), A306157 (b=3), this sequence (b=4), A306159 (b=5).
%Y A306158 Cf. A000302, A038069.
%K A306158 nonn
%O A306158 1,1
%A A306158 _Seiichi Manyama_, Jun 23 2018