A131057 Least nonnegative k such that n!-k is semiprime.

0, 2, 1, 2, 7, 1, 2, 1, 5, 3, 1, 19, 11, 1, 19, 19, 11, 1, 19, 23, 1, 1, 47, 1, 1, 29, 3, 29, 2, 59, 73, 1, 43, 1, 13, 17, 41, 1, 2, 5, 3, 53, 79, 7, 1, 53, 23, 1, 13, 13, 61, 7, 59, 61, 7, 31, 1, 89, 107, 103, 67, 47, 103, 19, 43, 1, 71, 11, 7, 83, 79, 67, 71

Offset

3,2

Comments

Semiprime analog of A033933. After n = 3, a(n) is never again 0.

Links

Table of n, a(n) for n=3..75.

Formula

a(n) = Min_{k such that n!-k is in A001358 and k>=0}.

Example

a(3) = 0 because 3! - 0 = 6 - 0 = 6 = 2 * 3.
a(4) = 2 because 4! - 2 = 24 - 2 = 22 = 2 * 11.
a(5) = 1 because 5! - 1 = 119 = 7 * 17.

Crossrefs

Cf. A001358, A033933, A356207.

Sequence in context: A114572 A052621 A212671 * A051852 A054495 A007966

Adjacent sequences: A131054 A131055 A131056 * A131058 A131059 A131060

Keyword

nonn

Author

Jonathan Vos Post, Sep 24 2007

Extensions

More terms from Jinyuan Wang, Aug 28 2022

Status

approved