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A049244 Smallest nonnegative value taken on by 5x^2 - ny^2 for an infinite number of integer pairs (x, y). 0
1, 2, 2, 1, 0, 5, 5, 5, 5, 5, 1, 5, 5, 5, 5, 4, 3, 2, 1, 0, 5, 5, 5, 5, 5, 5, 2, 5, 5, 5, 1, 5, 3, 5, 5, 5, 5, 5, 5, 5, 1, 3, 2, 1, 0, 5, 5, 5, 5, 5, 5, 5, 3, 5, 5, 5, 5, 5, 1, 5, 1, 2, 5, 5, 5, 5, 2, 5, 5, 5, 1, 5, 5, 5, 5, 4, 3, 2, 1, 0, 5, 5, 2, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 3, 5, 5, 1, 5, 5, 5, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..105.

MATHEMATICA

f[n_, z_] := FindInstance[x > 0 && y > 0 && 5*x^2 - n*y^2 == z, {x, y}, Integers, 1]; a[n_] := For[z = 0, z <= 5, z = z + GCD[n, 5], fz = f[n, z]; If[fz =!= {}, Print["a(", n, ") = ", z, " {x, y} = ", {x, y} /. fz[[1]]]; Return[z]]];

a[49] := (Print["a(49) = ", 5, " {x, y} = ", {51841, 16560}]; 5);

a[81] := (Print["a(81) = ", 5, " {x, y} = ", {161, 40}]; 5);

a[83] := (Print["a(83) = ", 5, " {x, y} = ", {1919, 471}]; 5);

a[98] := (Print["a(98) = ", 3, " {x, y} = ", {31, 7}]; 3);

Table[TimeConstrained[a[n], 300], {n, 1, 105}] (* Jean-Fran├žois Alcover, Oct 10 2016 *)

CROSSREFS

Sequence in context: A106566 A099039 A205574 * A110281 A120059 A067347

Adjacent sequences:  A049241 A049242 A049243 * A049245 A049246 A049247

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified February 17 16:26 EST 2018. Contains 299296 sequences. (Running on oeis4.)