OFFSET
1,1
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
KEYWORD
nonn
AUTHOR
Colin Barker, Feb 10 2014
STATUS
approved