E.g.f.: 1/Product_{k>=1} (1 + x^k/k!).

Terms

a(0) =1a(1) =-1a(2) =1a(3) =-4a(4) =21a(5) =-96a(6) =520a(7) =-3795a(8) =32053a(9) =-284368a(10) =2763876a(11) =-30648465a(12) =373339824a(13) =-4833294389a(14) =67167087793