A108154 a(n) = n^2 - n + 1 if prime else 0.

0, 3, 7, 13, 0, 31, 43, 0, 73, 0, 0, 0, 157, 0, 211, 241, 0, 307, 0, 0, 421, 463, 0, 0, 601, 0, 0, 757, 0, 0, 0, 0, 0, 1123, 0, 0, 0, 0, 1483, 0, 0, 1723, 0, 0, 0, 0, 0, 0, 0, 0, 2551, 0, 0, 0, 2971, 0, 0, 3307, 0, 3541, 0, 0, 3907, 0, 0, 0, 4423, 0, 0, 4831, 0, 5113, 0, 0, 0, 5701, 0

Offset: 1

Author

Pierre CAMI, Jun 06 2005

Keywords

• easy
• nonn

Examples

			1^2 - 1 + 1 = 1, which is not prime, so a(1)=0;
2^2 - 2 + 1 = 3, which is prime, so a(2)=3;
3^3 - 3 + 1 = 7, which is prime, so a(3)=7.
		

Crossrefs

Cf. A002061, A002383, A002384.

Programs

Mathematica

f[n_] := Block[{p = n^2 - n + 1}, If[ PrimeQ[p], p, 0]]; Table[ f[n], {n, 77}] (* Robert G. Wilson v, Jun 07 2005 *)

PARI

vector(80, n, if (isprime(p=n^2-n+1), p, 0)) \\ Michel Marcus, Jul 31 2015

Extensions

More terms from Robert G. Wilson v, Jun 07 2005