A289851 Primes of the form k!2 - 8, where k!2 is the double factorial number (A006882).

7, 97, 937, 654729067, 13113070457687988603440617, 563862029680583509947946867, 536347102817482913555411512425352545980058003572241486357421867, 352999527454840466971061863960307904899505075341088595453568994140617

Offset: 1

Author

Robert Price, Jul 13 2017

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..10
• Henri and Renaud Lifchitz, PRP Records.Search for n!2-8.
• Joe McLean, Interesting Sources of Probable Primes.
• OpenPFGW Project, Primality Tester.

Crossrefs

Cf. A006882, A259359.

Programs

Mathematica

MultiFactorial[n_, k_] := If[n<1, 1, n*MultiFactorial[n-k, k]];
Select[Table[MultiFactorial[i, 2] - 8, {i, 5, 100}], PrimeQ[#]&]
Select[Range[5,100]!!-8,PrimeQ] (* Harvey P. Dale, Feb 06 2024 *)

Formula

a(n) = A006882(A259359(n)) - 8. - Elmo R. Oliveira, Apr 14 2025

Extensions

Definition corrected by Harvey P. Dale, Feb 06 2024