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 A049247 Smallest nonnegative value taken on by 8x^2 - ny^2 for an infinite number of integer pairs (x, y). 0

%I

%S 4,0,5,4,3,2,1,0,8,8,8,8,8,2,8,8,4,0,8,8,8,2,1,8,7,6,5,4,3,2,1,0,8,8,

%T 8,8,8,2,8,8,8,8,5,8,8,2,1,8,4,0,8,8,3,2,8,8,8,8,8,8,8,2,8,8,7,6,5,4,

%U 3,2,1,0,8,8,8,8,8,8,1,8,8,8,5,8,8,2,8,8,8,8,8,4,8,2,8,8,4,0,8,8,3,2,1,8,8

%N Smallest nonnegative value taken on by 8x^2 - ny^2 for an infinite number of integer pairs (x, y).

%t p = 8; 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], Which[n == 49, z = 4; fz = \$Aborted, n == 81, z = 8; fz = \$Aborted, n == 83, z = 5; fz = \$Aborted, n == 101, z = 3; fz = \$Aborted, True, 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-François Alcover_, Oct 11 2016 *)

%K nonn

%O 1,1

%A _David W. Wilson_

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Last modified August 12 08:33 EDT 2020. Contains 336438 sequences. (Running on oeis4.)