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 A301469 #5 Mar 23 2018 20:53:04
%S A301469 2,-1,1,0,0,1,0,1,1,1,2,3,3,6,7,11,17,23,35,53,75,119,173,264,398,603,
%T A301469 911,1411,2114,3279,4977,7696,11760,18253,27909,43451,66675,103945,
%U A301469 160096,249904,385876,603107,933474,1461967,2266384,3553167,5521053,8664117,13485744
%N A301469 Signed recurrence over enriched r-trees: a(n) = 2 * (-1)^n + Sum_y Product_{i in y} a(y) where the sum is over all integer partitions of n - 1.
%F A301469 O.g.f.: 2/(1 + x) + x Product_{i > 0} 1/(1 - a(i) x^i).
%F A301469 a(n) = Sum_t 2^k * (-1)^w where the sum is over all enriched r-trees of size n, k is the number of leaves, and w is the sum of leaves.
%t A301469 a[n_]:=a[n]=2(-1)^n+Sum[Times@@a/@y,{y,IntegerPartitions[n-1]}];
%t A301469 Array[a,30]
%Y A301469 Cf. A032305, A055277, A093637, A127524, A196545, A220418, A273866, A273873, A289501, A290261, A290973, A301342-A301345, A301364-A301368, A301422, A301462, A301467, A301470.
%K A301469 sign
%O A301469 0,1
%A A301469 _Gus Wiseman_, Mar 21 2018