A072900 Discriminant of quadratic field Q(sqrt(prime(n))) where prime(n) is the n-th prime.

8, 12, 5, 28, 44, 13, 17, 76, 92, 29, 124, 37, 41, 172, 188, 53, 236, 61, 268, 284, 73, 316, 332, 89, 97, 101, 412, 428, 109, 113, 508, 524, 137, 556, 149, 604, 157, 652, 668, 173, 716, 181, 764, 193, 197, 796, 844, 892, 908, 229, 233, 956, 241, 1004, 257, 1052

Offset: 1

Author

Benoit Cloitre, Aug 10 2002

Keywords

• easy
• nonn

Crossrefs

a(n) = A037449(A000040(n)).

Programs

Mathematica

If[Mod[#,4]==1,#,4#]&/@Prime[Range[60]] (* Harvey P. Dale, Jul 26 2015 *)

PARI

a(n)=if(n<0,0,coredisc(prime(n)))

Formula

a(n) = if prime(n)=4k+1 then prime(n) else prime(n)*4.

a(n) = (3*floor((prime(n) mod 4)/2) + 1)*prime(n). - Reinhard Zumkeller, Aug 20 2002