a(n) = number of nonempty subsets S of {1,2,...,n} such that (number of nonprimes in S) = (number of primes in S).

A369854

a(n) = number of nonempty subsets S of {1,2,...,n} such that (number of nonprimes in S) = (number of primes in S).

Terms

    a(0) =0a(1) =0a(2) =1a(3) =2a(4) =5a(5) =9a(6) =19a(7) =34a(8) =69a(9) =125a(10) =209a(11) =461a(12) =791a(13) =1715a(14) =3002a(15) =5004a(16) =8007a(17) =19447a(18) =31823a(19) =75581a(20) =125969a(21) =203489a(22) =319769a(23) =817189a(24) =1307503a(25) =2042974a(26) =3124549a(27) =4686824a(28) =6906899a(29) =20030009

External references