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 A066159 Numbers n such that 4n-1 divides (2n-1)! + 1. 2

%I

%S 2,3,5,11,12,17,20,26,32,33,41,45,48,50,57,66,87,92,96,105,108,111,

%T 120,123,126,131,141,143,150,152,155,158,171,173,182,185,186,197,206,

%U 210,216,222,237,248,255,263,272,273,281,288,297,323,330,342

%N Numbers n such that 4n-1 divides (2n-1)! + 1.

%H Harry J. Smith, <a href="/A066159/b066159.txt">Table of n, a(n) for n=1..1000</a>

%H Ed Pegg, Jr., <a href="http://www.mathpuzzle.com/25Feb.htm">Math. Puzzles</a> (Material added Dec 11 2001)

%p A066159:=n->`if`((2*n-1)!+1 mod (4*n-1) = 0, n, NULL): seq(A066159(n), n=1..500); # _Wesley Ivan Hurt_, Dec 01 2015

%t Select[Range@ 360, Divisible[(2 # - 1)! + 1, 4 # - 1] &] (* _Michael De Vlieger_, Dec 02 2015 *)

%o (PARI) { n=0; for (m=1, 10^9, if (frac(((2*m - 1)! + 1)/(4*m - 1)) == 0, write("b066159.txt", n++, " ", m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Feb 03 2010

%Y Cf. A066160.

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Dec 13 2001

%E Reference into the Math Puzzles made more specific by _R. J. Mathar_, Feb 11 2010

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Last modified November 24 07:30 EST 2020. Contains 338607 sequences. (Running on oeis4.)