-1 + Product_{n>=1} (1 + x^n)^a(n) = g.f. of A000040 (prime numbers).

Terms

a(0) =2a(1) =2a(2) =1a(3) =2a(4) =2a(5) =-2a(6) =2a(7) =-2a(8) =4a(9) =-1a(10) =4a(11) =-7a(12) =10a(13) =-19a(14) =20a(15) =-20a(16) =34a(17) =-42a(18) =64a(19) =-100a(20) =126a(21) =-178a(22) =258a(23) =-326a(24) =464a(25) =-675a(26) =936a(27) =-1371a(28) =1888a(29) =-2550