A247865 Numbers n such that n!3 + 3^2 is prime.

2, 4, 5, 7, 8, 14, 17, 19, 22, 23, 26, 34, 46, 59, 70, 86, 100, 101, 118, 148, 151, 160, 200, 281, 317, 343, 682, 842, 853, 871, 1244, 1988, 2170, 2389, 2728, 3049, 3661, 4678, 9169, 12767, 16072, 19808, 20710, 33142, 33442

Offset

1,1

Comments

Large terms correspond to probable primes.

a(46) > 50000.

Links

Table of n, a(n) for n=1..45.

Henri & Renaud Lifchitz, PRP Records. Search for n!3+9

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Eric Weisstein's World of Mathematics, Multifactorial.

Example

8!3+9 = 8*5*2+9= 89 is prime, so 8 is in the sequence.

Mathematica

MultiFactorial[n_, k_] := If[n < 1, 1, If[n < k + 1, n, n*MultiFactorial[n - k, k]]];
lst={}; Do[If[PrimeQ[MultiFactorial[n, 3] + 9], AppendTo[lst, n]], {n, 100}]; lst

Crossrefs

Cf. A007661, A037082, A084438, A243078.

Sequence in context: A272195 A082672 A241808 * A271505 A343915 A187054

Adjacent sequences: A247862 A247863 A247864 * A247866 A247867 A247868

Keyword

nonn,more

Author

Robert Price, Sep 25 2014

Status

approved