A216513 Number of nonnegative integer solutions to the equation x^2 + 6*y^2 = n.

1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 2, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 1, 2, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 2, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0

Offset

0,26

Links

Table of n, a(n) for n=0..99.

Mathematica

r[n_] := Reduce[x >= 0 && y >= 0 && x^2 + 6 y^2 == n, Integers];
a[n_] := Which[rn = r[n]; rn === False, 0, Head[rn] === And, 1, Head[rn] === Or, Length[rn], True, -1];
Table[a[n], {n, 0, 99}] (* Jean-François Alcover, Jun 24 2017 *)

Crossrefs

Cf. A002481.

Sequence in context: A253786 A078595 A301989 * A364419 A291437 A302231

Adjacent sequences: A216510 A216511 A216512 * A216514 A216515 A216516

Keyword

nonn

Author

V. Raman, Sep 08 2012

Extensions

Verified by N. J. A. Sloane, Sep 10 2012

a(96) and a(97) corrected by Jean-François Alcover, Jun 24 2017

Status

approved