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

1,3

Links

Table of n, a(n) for n=1..69.

Example

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.

Sequence in context: A005074 A161564 A078182 * A363803 A133394 A305628

Adjacent sequences: A076197 A076198 A076199 * A076201 A076202 A076203

Keyword

nonn

Author

Zak Seidov, Nov 02 2002

Extensions

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

Status

approved