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

1,1

Links

Table of n, a(n) for n=1..56.

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

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A114404 A173457 A033198 * A203836 A220665 A166173

Adjacent sequences: A072897 A072898 A072899 * A072901 A072902 A072903

Keyword

easy,nonn

Author

Benoit Cloitre, Aug 10 2002

Status

approved