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%I #14 Jan 09 2015 08:56:44
%S 7,13,17,19,28,41,52,61,63,68,73,76,77,83,101,112,117,131,139,143,153,
%T 161,164,167,171,173,175,187,208,209,227,241,244,252,259,271,272,283,
%U 292,293,299,304,307,308,325,332,343,349,369,371,391,404,409,425,437
%N Positive integers k such that x^2 - 9xy + y^2 + k = 0 has integer solutions.
%e 7 is in the sequence because x^2 - 9xy + y^2 + 7 = 0 has integer solutions, for example (x, y) = (1, 8).
%o (PARI) is(n)=bnfisintnorm(bnfinit(x^2-9*x+1),-n) \\ _Ralf Stephan_, Feb 11 2014
%Y Cf. A070998 (k = 7).
%Y Cf. A031363, A084917, A237351, A237599, A237606, A237610.
%K nonn
%O 1,1
%A _Colin Barker_, Feb 10 2014
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