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A049246 Smallest nonnegative value taken on by 7x^2 - ny^2 for an infinite number of integer pairs (x, y). 0

%I

%S 3,5,1,3,2,1,0,7,7,2,7,4,2,7,3,7,7,7,1,7,7,6,5,4,3,2,1,0,7,7,1,7,7,7,

%T 7,7,3,1,7,7,7,7,3,7,7,7,1,7,7,7,3,7,7,1,7,7,6,5,1,3,2,1,0,7,7,7,7,7,

%U 7,7,7,7,7,7,7,4,7,7,3,7,7,7,1,7,3,7,1,7,7,7,7,7,7,1,5,7,7,7,7,3,2,6,1,7,7

%N Smallest nonnegative value taken on by 7x^2 - ny^2 for an infinite number of integer pairs (x, y).

%t p = 7; f[n_, z_] := FindInstance[x > 0 && y > 0 && p*x^2 - n*y^2 == z, {x, y}, Integers, 1]; a[n_] := For[z = 0, z <= p, z = z + GCD[n, p], Switch[n, 64 | 81, z = p; fz = $Aborted, _, 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, 105}] (* _Jean-Fran├žois Alcover_, Oct 11 2016 *)

%K nonn

%O 1,1

%A _David W. Wilson_

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Last modified September 19 10:41 EDT 2020. Contains 337178 sequences. (Running on oeis4.)