OFFSET
1,2
COMMENTS
Partials sums of number of labeled Eulerian digraphs with n nodes. The subsequence of primes in this partial sum begins: 3, 13, 7901, 1383853, 17660268902020093.
FORMULA
a(n) = SUM[i=1..n] A007080(i).
EXAMPLE
a(5) = 1 + 2 + 10 + 152 + 7736 = 7901 is prime.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Apr 15 2010
STATUS
approved