

A031396


Numbers k such that Pell equation x^2  k*y^2 = 1 is soluble.


17



1, 2, 5, 10, 13, 17, 26, 29, 37, 41, 50, 53, 58, 61, 65, 73, 74, 82, 85, 89, 97, 101, 106, 109, 113, 122, 125, 130, 137, 145, 149, 157, 170, 173, 181, 185, 193, 197, 202, 218, 226, 229, 233, 241, 250, 257, 265, 269, 274, 277, 281, 290, 293, 298
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OFFSET

1,2


COMMENTS

Terms are divisible neither by 4 nor by a prime of the form 4*k + 3 (although these conditions are not sufficient  compare A031398).  Lekraj Beedassy, Aug 17 2005


REFERENCES

Harvey Cohn, "Advanced Number Theory".


LINKS



MATHEMATICA

fQ[n_] := Solve[x^2 + 1 == n*y^2, {x, y}, Integers] != {}; Select[ Range@ 300, fQ] (* Robert G. Wilson v, Dec 19 2013 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



