login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Numbers k for which (10+k!)/10 is prime.
21

%I #14 Nov 08 2016 17:02:50

%S 5,6,11,12,15,23,26,37,45,108,112,129,137,148,172,248,760,807,975,

%T 1398,5231,8765,24182

%N Numbers k for which (10+k!)/10 is prime.

%C Primes of the form (10+k!)/10 see A139070.

%C a(24) > 25000. - _Robert Price_, Nov 08 2016

%t a = {}; Do[If[PrimeQ[(n! + 10)/10], AppendTo[a, n]], {n, 1, 500}]; a

%o (PARI) for(k=5,1e3,if(ispseudoprime(k!/10+1),print1(k", "))) \\ _Charles R Greathouse IV_, Jul 15 2011

%Y Cf. A082672, A089085, A089130, A117141, A007749, A139056, A139057, A139058, A139059, A139060, A139061, A139061, A139062, A139063, A139064, A139065, A139066, A020458, A139068, A137390, A139070, A139071, A139072.

%Y 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).

%K nonn

%O 1,1

%A _Artur Jasinski_, Apr 07 2008

%E More terms from _Serge Batalov_, Feb 18 2015

%E a(22)-a(23) from _Robert Price_, Nov 08 2016