A137390 Numbers k for which (9 + k!)/9 is prime.

8, 46, 87, 168, 259, 262, 292, 329, 446, 1056, 3562, 11819, 26737

Offset: 1

Author

Artur Jasinski, Apr 09 2008

Keywords

• nonn
• more

Comments

No other k exists, for k <= 6000. - Dimitris Zygiridis (dmzyg70(AT)gmail.com), Jul 25 2008

The next number in the sequence, if one exists, is greater than 10944. - Robert Price, Mar 16 2010

Borrowing from A139074 another term in this sequence is 26737. There may be others between 10944 and 26737. - Robert Price, Dec 13 2011

There are no other terms for k < 26738. - Robert Price, Feb 10 2012

Examples

			a(11) = 3562 because 3562 is the 11th natural number for which k!/9 + 1 is prime. 3562 is the new term.
		

Crossrefs

Cf. A139068 (primes of the form (9 + k!)/9).

Cf. k!/m - 1 is a prime: A002982, A082671, A139056, A139199-A139205.

Cf. (m + k!)/m is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A139071.

Programs

Mathematica

a = {}; Do[If[PrimeQ[(n! + 9)/9], AppendTo[a, n]], {n, 1, 500}]; a

PARI

for(n=6,1e4,if(ispseudoprime(n!/9+1),print1(n", "))) \\ Charles R Greathouse IV, Jul 15 2011

PFGW

ABC2 $a!/9+1
a: from 6 to 1000 // Jinyuan Wang, Feb 04 2020

Extensions

Edited by N. J. A. Sloane, May 15 2008 at the suggestion of R. J. Mathar

a(10) corrected from 1053 to 1056 by Dmitry Kamenetsky, Jul 12 2008

a(11) from Dimitris Zygiridis (dmzyg70(AT)gmail.com), Jul 25 2008

a(12)-a(13) from Robert Price, Feb 10 2012