A247044 Least number k > 0 such that k!*n! - 1 is prime.

3, 2, 1, 1, 2, 1, 1, 3, 6, 7, 14, 1, 8, 1, 2, 4, 2, 5, 16, 26, 27, 2, 18, 29, 9, 15, 7, 2, 24, 1, 44, 1, 1, 209, 12, 128, 20, 1, 18, 5, 6, 3, 21, 5, 42, 6, 45, 19, 14, 10, 8, 20, 72, 8, 226, 11, 5, 77, 99, 28, 16, 15, 157, 9, 24, 17, 110, 9, 28, 26, 16, 37, 163, 79, 29, 45, 58, 21, 66

Offset

1,1

Comments

If a(n) = K, a(K) <= n for all n.

a(n) = 1 if and only if n is in A002982.

Links

Table of n, a(n) for n=1..79.

Prog

(PARI)
a(n)=k=1; while(!ispseudoprime(k!*n!-1), k++); k
n=1; while(n<100, print1(a(n), ", "); n++)

Crossrefs

Cf. A002982, A231549.

Sequence in context: A350942 A140056 A240239 * A083663 A085427 A172130

Adjacent sequences: A247041 A247042 A247043 * A247045 A247046 A247047

Keyword

nonn

Author

Derek Orr, Sep 10 2014

Status

approved