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Numbers n for which (8+n!)/8 is prime.
20

%I #13 Dec 21 2016 02:50:06

%S 7,9,10,12,14,20,23,24,29,44,108,2049,3072,4862,8807,15089

%N Numbers n for which (8+n!)/8 is prime.

%C a(17) > 25000. - _Robert Price_, Dec 20 2016

%t a = {}; Do[If[PrimeQ[(n! + 8)/8], AppendTo[a, n]], {n, 1, 500}]; a

%o (PARI) is(n)=n>6 && isprime((8+n!)/8) \\ _Charles R Greathouse IV_, Apr 29 2016

%Y For primes of the form (8+k!!)/8 see A139066.

%Y Cf. A089130, A117141, A139035, A139057, A139059, A139060, A139062, A139064, A139067.

%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; definition corrected Feb 24 2010.

%E More terms from _Serge Batalov_, Feb 18 2015

%E a(15)-a(16) from _Robert Price_, Dec 20 2016