A173416 Exactly one of 2n^2-1 and 2n^2+1 is prime.

1, 2, 4, 7, 8, 9, 10, 11, 13, 15, 17, 18, 22, 25, 27, 28, 30, 33, 34, 38, 39, 41, 43, 46, 49, 50, 52, 56, 59, 62, 63, 64, 66, 69, 72, 73, 75, 76, 80, 81, 85, 91, 92, 93, 95, 96, 98, 99, 105, 108, 109, 112, 113, 115, 118, 123, 125, 126, 127, 134, 135, 137, 140, 141, 143

Offset: 1

Author

Juri-Stepan Gerasimov, Mar 01 2010

Keywords

• nonn

Comments

Numbers in A089001 or in A066049 but not in both. [From R. J. Mathar, Mar 09 2010]

Examples

			a(1)=1 because 2*1^2-1=1 is nonprime and 2*1^2+1=3 is prime.
		

Extensions

37 removed by R. J. Mathar, Mar 09 2010