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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 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.)