A139065 Numbers k for which (7+k!)/7 is prime.

11, 15, 16, 25, 35, 59, 64, 68, 82, 121, 149, 238, 584, 912, 3349, 4111, 4324, 15314, 19944, 20658, 22740, 23364

Offset

1,1

Comments

For primes of the form (7+k!)/7, see A139064.

a(23) > 25000. - Robert Price, Nov 20 2016

Links

Table of n, a(n) for n=1..22.

Mathematica

a = {}; Do[If[PrimeQ[(n! + 7)/7], AppendTo[a, n]], {n, 1, 500}]; a
Select[Range[500], PrimeQ[(7+#!)/7]&] (* Harvey P. Dale, Sep 01 2014 *)

Prog

(PARI) for(k=7, 1e3, if(ispseudoprime(k!/7+1), print1(k", "))) \\ Charles R Greathouse IV, Jul 15 2011

Crossrefs

Cf. A082672, A089085, A089130, A117141, A007749, A139056, A139057, A139058, A139059, A139060, A139061, A139061, A139062, A139063, A139064, A139065, A139066, A020458.

Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1<=m<=10).

Sequence in context: A174952 A209898 A371553 * A365329 A186404 A111322

Adjacent sequences: A139062 A139063 A139064 * A139066 A139067 A139068

Keyword

nonn,hard,more

Author

Artur Jasinski, Apr 07 2008

Extensions

More terms from Serge Batalov, Feb 18 2015

a(18)-a(22) from Robert Price, Nov 20 2016

Status

approved