%I
%S 3,5,7,9,13,19,21,23,27,29,35,47,49,51,55,57,61,65,69,75,77,83,85,91,
%T 97,99,105,111,117,125,127,133,135,149,161,163,173,177,181,183,187,
%U 191,211,217,239,247,251,257,259,273,281,285,295,307,313,315,317,329,331,341
%N Numbers n such that (3n^2+1)/4 is prime.
%F a(n)=(4*A002407(n)1)/3
%t Select[Range[400],PrimeQ[(3#^2+1)/4]&] (* _Harvey P. Dale_, Mar 24 2011 *)
%o (PARI) is(n)=isprime((3*n^2+1)/4) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. comment by Michael Somos in A002407.
%K nonn,easy
%O 1,1
%A _Zak Seidov_, Aug 23 2006
