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 A174432 #2 Mar 30 2012 18:40:51 %S A174432 1,2,6,33,281,3111,41343,635202,11036914,213638812,4555901812, %T A174432 106107724162,2679887230354,72962091956750,2130453028323070, %U A174432 66421485491085025,2202438789394598209,77400308039913410963 %N A174432 Partial sums of A000699. %C A174432 Partial sums of number of irreducible diagrams (in the sense of perturbation expansion in quantum field theory: spinor case in 4 spacetime dimensions) with 2n nodes. The subsequence of primes in this partial sum begins: 2, 281, and there never seem to be any more, as the underlying sequence is all even after A000699(8). %F A174432 a(n) = SUM[i=1..n] A000699(i), where those A000699(n) = (n-1)*SUM[i=1..n-1] A000699(i)*A000699(n-i). %e A174432 a(18) = 1 + 1 + 4 + 27 + 248 + 2830 + 38232 + 593859 + 10401712 + 202601898 + 4342263000 + 101551822350 + 2573779506192 + 70282204726396 + 2057490936366320 + 64291032462761955 + 2136017303903513184 + 75197869250518812754. %Y A174432 Cf. A000699, A004300, A051862. %K A174432 easy,nonn %O A174432 1,2 %A A174432 _Jonathan Vos Post_, Mar 19 2010