A289852 Primes of the form k!2 - 16, where k!2 is the double factorial number (A006882).

89, 929, 135119, 34459409, 7905853580609, 669325572332691496707919692320662308340434243618803739488329723923351785805848442856791239207612629457179653299076271283992814866750698368061459208762618124485015869140609

Offset: 1

Author

Robert Price, Jul 13 2017

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..7
• Henri and Renaud Lifchitz, PRP Records.Search for n!2-16.
• Joe McLean, Interesting Sources of Probable Primes.
• OpenPFGW Project, Primality Tester.

Crossrefs

Cf. A006882, A258616.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 2] - 16, {i, 6, 100}], PrimeQ[#]&]

Formula

a(n) = A006882(A258616(n)) - 16. - Elmo R. Oliveira, Apr 14 2025