A231549 -id:A231549 - cp's OEIS frontend

A231901 Least k > n such that k!/n! + 1 is a prime, or 0 if no such k exists.

1, 2, 4, 4, 6, 6, 11, 9, 11, 10, 20, 12, 15, 15, 16, 16, 18, 18, 23, 21, 22, 22, 40, 25, 27, 31, 28, 28, 37, 30, 42, 38, 34, 36, 42, 36, 110, 39, 43, 40, 42, 42, 56, 46, 50, 46, 55, 65, 51, 51, 53, 52, 55, 55, 73, 58, 58, 58, 60, 60, 63, 63, 177, 68, 70, 66, 82, 72

Offset: 0

Alex Ratushnyak, Nov 15 2013

nonn

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Cf. A002981, A035093, A057217, A075757, A075758, A231549.

Table[k = n + 1; While[! PrimeQ[k!/n! + 1], k++]; k, {n, 100}] (* T. D. Noe, Nov 18 2013 *)

a(n) = {my(m = n+1); while(! isprime(m!/n! +1), m++); m;} \\ Michel Marcus, Mar 07 2014; corrected Jun 13 2022

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

Original entry on oeis.org

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

Derek Orr, Sep 10 2014

nonn

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

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

Cf. A002982, A231549.

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

cp's OEIS Frontend

A231901 Least k > n such that k!/n! + 1 is a prime, or 0 if no such k exists.

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