A247464 Numbers n such that n!!! - 3^4 is prime.

10, 13, 14, 17, 20, 26, 29, 31, 32, 50, 59, 77, 82, 104, 164, 185, 217, 263, 293, 361, 437, 442, 545, 547, 599, 608, 623, 739, 782, 1081, 1120, 1138, 1429, 2516, 2518, 4277, 4529, 5438, 5596, 11945, 12716, 13955, 14540, 31730, 31769, 42964, 46396

Offset

1,1

Comments

Large terms correspond to probable primes.

a(48) > 50000.

Links

Table of n, a(n) for n=1..47.

Henri & Renaud Lifchitz, PRP Records. Search for n!3-81

Joe McLean, Interesting Sources of Probable Primes

OpenPFGW Project, Primality Tester

Eric Weisstein's World of Mathematics, Multifactorial

Example

10!3-81 = 10*7*4*1-81 = 199 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] - 81], AppendTo[lst, n]], {n, 100}]; lst

Crossrefs

Cf. A007661, A037082, A084438, A243078.

Sequence in context: A226778 A061837 A256477 * A219110 A226024 A134651

Adjacent sequences: A247461 A247462 A247463 * A247465 A247466 A247467

Keyword

nonn,more

Author

Robert Price, Sep 17 2014

Status

approved