A247465 Numbers n such that n!3 - 3^5 is prime.

10, 19, 28, 50, 67, 77, 89, 112, 139, 146, 184, 194, 233, 310, 311, 388, 886, 1139, 1648, 1694, 2405, 2554, 3709, 4015, 5410, 5908, 6407, 8065, 9061, 9875, 11722, 13471, 26026, 26656, 29441, 32741

Offset

1,1

Comments

Large terms correspond to probable primes.

a(37) > 50000.

Links

Table of n, a(n) for n=1..36.

Henri & Renaud Lifchitz, PRP Records. Search for n!3-243

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Eric Weisstein's World of Mathematics, Multifactorial

Example

10!3-243 = 10*7*4*1-243 = 37 is prime, so 10 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] - 243], AppendTo[lst, n]], {n, 100}]; lst

Crossrefs

Cf. A007661, A037082, A084438, A243078.

Sequence in context: A017173 A326833 A276871 * A349548 A088410 A179110

Adjacent sequences: A247462 A247463 A247464 * A247466 A247467 A247468

Keyword

nonn,more

Author

Robert Price, Sep 17 2014

Status

approved