login
Values n such that prime(2*n) mod 12 == 5.
8

%I #16 Apr 12 2018 14:38:27

%S 5,8,12,13,15,20,30,31,33,49,51,52,54,58,63,70,71,74,76,79,80,81,85,

%T 88,89,92,93,97,98,103,106,109,110,117,119,126,134,135,144,145,148,

%U 149,151,156,160,165,166,169,171,175,178,181,191,192,196,199,200,201,202,204

%N Values n such that prime(2*n) mod 12 == 5.

%C Eight sets of integers (this, A116610 and A116612-A116617), dealing with the remainder classes {1,5,7,11} modulo 12 are inspired by the Taylor series of sin(x) = x-x^3/3!+x^5/5!-... and cos(x)=1-x^2/2!+x^4/4!-x^6/6!+... which might be constructed via partitioning of the series terms according to factorial denominators of 2n+1 = 1,3,5,7,.. and 2n=1,2,4,6,...

%H G. C. Greubel, <a href="/A116602/b116602.txt">Table of n, a(n) for n = 1..5000</a>

%F A116602 = 1/2 * {even terms in A160591}. - _M. F. Hasler_, May 22 2009

%e 33 is in the sequence because the 66th prime is 317 and 317 mod 12=5.

%p a:=proc(n) if ithprime(2*n) mod 12 = 5 then n fi end: seq(a(n),n=1..220);

%t a[1] = Flatten[Table[If[Mod[Prime[2*n], 12] == 5, n, {}], {n, 1, 100}]]

%t Select[Range[210],Mod[Prime[2#],12]==5&] (* _Harvey P. Dale_, Apr 12 2018 *)

%o (PARI) for(n=1,999, prime(2*n)%12==5 & print1(n",")) \\ _M. F. Hasler_, May 22 2009

%K nonn,easy

%O 1,1

%A _Roger L. Bagula_, Mar 29 2006

%E Edited by _N. J. A. Sloane_, Apr 05 2006, May 22 2009