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A237609 Positive integers k such that x^2 - 9xy + y^2 + k = 0 has integer solutions. 8
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

EXAMPLE

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

PROG

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

CROSSREFS

Cf. A070998 (k = 7).

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

Sequence in context: A079697 A079695 A079698 * A038906 A097959 A156543

Adjacent sequences:  A237606 A237607 A237608 * A237610 A237611 A237612

KEYWORD

nonn

AUTHOR

Colin Barker, Feb 10 2014

STATUS

approved

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Last modified September 19 06:21 EDT 2021. Contains 347551 sequences. (Running on oeis4.)