

A139056


Numbers k for which (k!3)/3 is prime.


56



4, 6, 12, 16, 29, 34, 43, 111, 137, 181, 528, 2685, 39477, 43697
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OFFSET

1,1


COMMENTS

Corresponding primes (k!3)/3 are in A139057.
a(13) > 10000. The PFGW program has been used to certify all the terms up to a(12), using a deterministic test which exploits the factorization of a(n) + 1.  Giovanni Resta, Mar 28 2014
98166 is a member of the sequence but its index is not yet determined. The interval where sieving and tests were not run is [60000,90000].  Serge Batalov, Feb 24 2015


LINKS

Table of n, a(n) for n=1..14.
C. Caldwell. The Prime database entry for the prime generated by a(i)=98166.


MATHEMATICA

a = {}; Do[If[PrimeQ[(3 + n!)/3], AppendTo[a, n]], {n, 1, 1000}]; a


PROG

(PARI) for(n=1, 1000, if(floor(n!/31)==n!/31, if(ispseudoprime(n!/31), print(n)))) \\ Derek Orr, Mar 28 2014


CROSSREFS

Cf. A007749, A117141.
Cf. n!/m1 is a prime: A002982, A082671, A139056, A139199A139205.
Cf. n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071.
Cf. m*n!1 is a prime: A076133, A076134, A099350, A099351, A180627A180631.
Cf. m*n!+1 is a prime: A051915, A076679A076683, A178488, A180626, A126896.
Sequence in context: A172445 A274221 A327479 * A152519 A240507 A022802
Adjacent sequences: A139053 A139054 A139055 * A139057 A139058 A139059


KEYWORD

nonn,more


AUTHOR

Artur Jasinski, Apr 07 2008


EXTENSIONS

Definition corrected by Derek Orr, Mar 28 2014
a(8)a(11) from Derek Orr, Mar 28 2014
a(12) from Giovanni Resta, Mar 28 2014
a(13)a(14) from Serge Batalov, Feb 24 2015


STATUS

approved



