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 A308245 #6 May 20 2019 02:45:21 %S A308245 1,1,1,2,4,8,16,34,76,168,368,838,1964,4544,10464,24658,58984,140072, %T A308245 331456,795834,1932228,4665304,11227280,27305882,66953236,163418448, %U A308245 397826496,976658846,2412163316,5935476672,14576596320,36023097266,89458468968 %N A308245 G.f.: x * Product_{k>=1} 1/(1 - a(k)*(-x)^k)^((-1)^k). %F A308245 Recurrence: a(n+1) = (1/n) * Sum_{k=1..n} ( Sum_{d|k} (-1)^(k+d)*d*a(d)^(k/d) ) * a(n-k+1). %t A308245 a[n_] := a[n] = SeriesCoefficient[x Product[1/(1 - a[k] (-x)^k)^((-1)^k), {k, 1, n - 1}], {x, 0, n}]; Table[a[n], {n, 1, 33}] %t A308245 a[n_] := a[n] = Sum[Sum[(-1)^(k + d) d a[d]^(k/d), {d, Divisors[k]}] a[n - k], {k, 1, n - 1}]/(n - 1); a[1] = 1; Table[a[n], {n, 1, 33}] %Y A308245 Cf. A032305, A045648, A049075, A093637, A308246. %K A308245 nonn %O A308245 1,4 %A A308245 _Ilya Gutkovskiy_, May 16 2019