A014202 Number of solutions to x^2 + x*y + y^2 <= n, excluding (0,0), divided by 6.

0, 1, 1, 2, 3, 3, 3, 5, 5, 6, 6, 6, 7, 9, 9, 9, 10, 10, 10, 12, 12, 14, 14, 14, 14, 15, 15, 16, 18, 18, 18, 20, 20, 20, 20, 20, 21, 23, 23, 25, 25, 25, 25, 27, 27, 27, 27, 27, 28, 31, 31, 31, 33, 33, 33, 33, 33, 35, 35, 35

Offset

0,4

Links

Table of n, a(n) for n=0..59.

Formula

For n > 0, a(n) = Sum_{k=1..n} K(k,3)*floor(n/k) where K(x,y) is the Kronecker symbol. - Benoit Cloitre, Oct 31 2009

Prog

(PARI) a(n)=if(n<1, 0, sum(k=1, n, kronecker(k, 3)*floor(n/k))) \\ Benoit Cloitre, Oct 31 2009

Crossrefs

A014201/6. Cf. A014200.

Sequence in context: A141784 A234337 A216391 * A309247 A238211 A338451

Adjacent sequences: A014199 A014200 A014201 * A014203 A014204 A014205

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved