A176837 Number of pairs (a, b) of positive integers with a < b such that both a^2 - nb and b^2 - na are squares

0, 0, 2, 1, 4, 2, 6, 5, 9, 4, 8, 13, 12, 6, 21, 18, 14, 9, 14, 28, 27

Offset

1,3

Links

Table of n, a(n) for n=1..21.

Example

A176837(3) = 2 because the pairs (5, 8) and (7, 11) have the specified property: 5^2 - 3*8 = 1^2, 8^2 - 3*5 = 7^2; 7^2 - 3*11 = 4^2, 11^2 - 3*7 = 10^2.

Crossrefs

A176837(n) = A176836(n) - A176835(n)

Sequence in context: A154280 A004795 A161268 * A339241 A007690 A239960

Adjacent sequences: A176834 A176835 A176836 * A176838 A176839 A176840

Keyword

nonn

Author

Jens Voß, Apr 27 2010

Status

approved