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A137390
Numbers k for which (9 + k!)/9 is prime.
50
8, 46, 87, 168, 259, 262, 292, 329, 446, 1056, 3562, 11819, 26737
OFFSET
1,1
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
EXAMPLE
a(11) = 3562 because 3562 is the 11th natural number for which k!/9 + 1 is prime. 3562 is the new term.
MATHEMATICA
a = {}; Do[If[PrimeQ[(n! + 9)/9], AppendTo[a, n]], {n, 1, 500}]; a
PROG
(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
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.
Sequence in context: A328198 A340975 A213132 * A190048 A034469 A212673
KEYWORD
nonn,more
AUTHOR
Artur Jasinski, Apr 09 2008
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
STATUS
approved