A066160 Numbers k such that 4k-1 divides (2k-1)! - 1.

1, 6, 8, 15, 18, 21, 27, 35, 38, 42, 53, 56, 60, 63, 68, 71, 77, 78, 83, 90, 95, 110, 116, 117, 122, 125, 137, 147, 161, 162, 165, 180, 188, 203, 207, 215, 221, 227, 228, 230, 242, 243, 246, 258, 260, 266, 276, 291, 293, 306, 308, 315, 320, 321

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n=1..1000

Ed Pegg, Jr., Math. Puzzles (Material added Dec 11 2001)

Maple

A066160:=n->`if`((2*n-1)! - 1 mod (4*n-1) = 0, n, NULL): seq(A066160(n), n=1..500); # Wesley Ivan Hurt, Dec 01 2015

Mathematica

Select[Range[350], Mod[(2 # - 1)! - 1, 4 # - 1] == 0 &] (* Vincenzo Librandi, Dec 02 2015 *)

Prog

(PARI) isok(k) = { ((2*k - 1)! - 1) % (4*k - 1) == 0 } \\ Harry J. Smith, Feb 03 2010
(Magma) [n: n in [1..350] |  (Factorial(2*n-1)-1) mod(4*n-1) eq 0]; // Vincenzo Librandi, Dec 02 2015

Crossrefs

Cf. A066159.

Sequence in context: A168610 A315919 A315920 * A315921 A315922 A315923

Adjacent sequences: A066157 A066158 A066159 * A066161 A066162 A066163

Keyword

nonn

Author

N. J. A. Sloane, Dec 13 2001

Status

approved