OFFSET
1,2
COMMENTS
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).
FORMULA
EXAMPLE
a(18) = 1 + 1 + 4 + 27 + 248 + 2830 + 38232 + 593859 + 10401712 + 202601898 + 4342263000 + 101551822350 + 2573779506192 + 70282204726396 + 2057490936366320 + 64291032462761955 + 2136017303903513184 + 75197869250518812754.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Mar 19 2010
STATUS
approved