A067241 Numbers k such that gcd((2*k)!+1, k!+1) > 1.

3, 5, 8, 9, 21, 23, 33, 39, 51, 63, 65, 81, 89, 95, 99, 113, 131, 173, 183, 191, 209, 215, 221, 239, 245, 251, 261, 281, 285, 299, 303, 309, 315, 341, 345, 363, 369, 371, 393, 411, 419, 431, 443, 473, 495, 509, 525, 543, 545, 561, 575, 593, 645, 659, 683, 711

Offset: 1

Author

Benoit Cloitre, Feb 20 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A038507, A127231.

Programs

Mathematica

q[k_] := !CoprimeQ[(2*k)!+1, k!+1]; Select[Range[720], q] (* Amiram Eldar, May 01 2025 *)

PARI

isok(k) = gcd((2*k)!+1, k!+1) > 1; \\ Amiram Eldar, May 01 2025