A076200 a(n) equals the least s>0 such that n!! + s^3 is prime, or 0 if there is no such prime.

1, 1, 2, 0, 2, 5, 2, 5, 2, 11, 4, 17, 8, 43, 2, 19, 2, 19, 4, 13, 32, 23, 4, 47, 2, 37, 74, 23, 86, 43, 122, 149, 128, 19, 146, 29, 226, 31, 64, 53, 2, 23, 134, 43, 268, 103, 134, 59, 64, 43, 4, 101, 16, 61, 346, 229, 278, 103, 16, 41, 64, 127, 2, 181, 302, 151, 146, 191, 262

Offset: 1

Author

Zak Seidov, Nov 02 2002

Keywords

• nonn

Examples

			a(4)=0 because 4!! = A006882(4) = 8 has algebraic factorization 8 + s^3 = (2 + s) * (4 - 2*s + s^2), thus can never be prime for any s. - _Sean A. Irvine_, Mar 24 2025
		

Crossrefs

Cf. A006882, A057019.

Extensions

Missing a(4)=0 inserted by Sean A. Irvine, Mar 24 2025