A108154 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..77.

EXAMPLE

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.

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 *)

PROG