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A049241 Smallest nonnegative value taken on by 2*x^2 - n*y^2 for an infinite number of integer pairs (x, y). 0
1, 0, 2, 2, 2, 2, 1, 0, 2, 2, 2, 2, 2, 2, 2, 2, 1, 0, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 1, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 1, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 0, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 0, 2, 2, 2, 2, 1, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

MATHEMATICA

f[n_, z_] := FindInstance[x > 0 && y > 0 && 2*x^2 - n*y^2 == z, {x, y}, Integers, 1]; a[n_] := For[z = 0, True, z = z + GCD[n, 2], fz = f[n, z]; If[fz =!= {}, Print["a(", n, ") = ", z, " {x, y} = ", {x, y} /. fz[[1]]]; Return[z]]]; a[81] := (Print["a(81) = ", 2, " {x, y} = ", {19601, 3080}]; 2); Table[TimeConstrained[a[n], 300], {n, 1, 105}] (* Jean-Fran├žois Alcover, Oct 09 2016 *)

CROSSREFS

Sequence in context: A318722 A174344 A340171 * A321858 A334235 A230415

Adjacent sequences:  A049238 A049239 A049240 * A049242 A049243 A049244

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified July 25 16:03 EDT 2021. Contains 346291 sequences. (Running on oeis4.)