A237609 Positive integers k such that x^2 - 9xy + y^2 + k = 0 has integer solutions.

7, 13, 17, 19, 28, 41, 52, 61, 63, 68, 73, 76, 77, 83, 101, 112, 117, 131, 139, 143, 153, 161, 164, 167, 171, 173, 175, 187, 208, 209, 227, 241, 244, 252, 259, 271, 272, 283, 292, 293, 299, 304, 307, 308, 325, 332, 343, 349, 369, 371, 391, 404, 409, 425, 437

Offset: 1

Author

Colin Barker, Feb 10 2014

Keywords

• nonn

Examples

			7 is in the sequence because x^2 - 9xy + y^2 + 7 = 0 has integer solutions, for example (x, y) = (1, 8).
		

Crossrefs

Cf. A070998 (k = 7).

Cf. A031363, A084917, A237351, A237599, A237606, A237610.

Programs

PARI

is(n)=bnfisintnorm(bnfinit(x^2-9*x+1),-n) \\ Ralf Stephan, Feb 11 2014