A307109 Number of integer solutions to x^2 + x*y + y^2 <= n excluding (0,0), divided by 2.

1, 1, 4, 5, 5, 5, 11, 11, 12, 12, 12, 15, 21, 21, 21, 22, 22, 22, 28, 28, 34, 34, 34, 34, 35, 35, 38, 44, 44, 44, 50, 50, 50, 50, 50, 51, 57, 57, 63, 63, 63, 63, 69, 69, 69, 69, 69, 72, 79, 79, 79, 85, 85, 85, 85, 85, 91, 91, 91, 91, 97, 97, 103, 104, 104, 104

Offset

1,3

Links

Table of n, a(n) for n=1..66.

Example

a(1)=a(2)=(2/2)=1: 2 solutions (-1,1),(1,-1);
a(3)=(8/2)=4: 2 solutions for n<3 and the 6 solutions (1,1), (-1,-1), (1,-2), (2,-1), (-1,2), (-2,1);
a(4)=a(5)=a(6)=10/2=5: 8 solutions for n<6 and the 2 solutions (-2,2), (2,-2).

Crossrefs

Cf. A014201, A014202, A198799, A230655, A300419.

Sequence in context: A141276 A088202 A238187 * A046780 A075129 A021691

Adjacent sequences: A307106 A307107 A307108 * A307110 A307111 A307112

Keyword

nonn

Author

Hugo Pfoertner, Mar 25 2019

Status

approved