A049264 - OEIS

%I #8 Oct 11 2016 16:03:14

%S 1,2,3,4,0,1,2,3,1,5,6,3,5,1,10,11,3,13,14,0,1,2,2,4,5,5,7,7,5,10,11,

%T 3,7,5,15,4,5,2,19,20,9,22,23,24,0,1,2,3,1,5,6,7,3,1,10,4,3,5,6,15,16,

%U 3,7,11,5,19,22,3,1,25,11,27,5,5,30,31,7,33,34,0,1,2,3,4,5,1,7,8,5,10,11

%N Smallest nonnegative value taken on by n*x^2 - 5*y^2 for an infinite number of integer pairs (x, y).

%t p = 5; f[n_, z_] := FindInstance[x > 0 && y > 0 && n*x^2 - p*y^2 == z, {x, y}, Integers, 1]; a[n_] := For[z = 0, True, z = z + GCD[n, p], fz = TimeConstrained[f[n, z], 300]; fz = If[fz === $Aborted, {{x -> Null, y -> Null}}, fz]; If[fz =!= {}, Print["a(", n, ") = ", z, " {x, y} = ", {x, y} /. fz[[1]]]; Return[z]]]; Table[a[n], {n, 1, 91}] (* _Jean-François Alcover_, Oct 11 2016 *)

%K nonn

%O 1,2

%A _David W. Wilson_