A374091 a(n) is the smallest nonnegative integer k where exactly n ordered pairs of positive integers (x, y) exist such that x^2 + 3*x*y + y^2 = k.

0, 5, 11, 605, 209, 73205, 2299, 8857805, 6061, 218405, 278179

Offset: 0

Author

Seiichi Manyama, Jun 28 2024

Keywords

• nonn
• more

Comments

a(n) is the smallest nonnegative k such that A374089(k) = n.

a(n) is of the form 5*k^2 if and only if n is odd.

a(12) = 66671.

a(14) = 5285401.

a(15) = 26427005.

a(16) = 187891.

a(18) = 1266749.

a(20) = 8067191.

a(21) = 3197667605. - Chai Wah Wu, Jun 29 2024

a(24) = 2066801.

a(26) = 36735721.

a(27) = 183678605. - Chai Wah Wu, Jun 28 2024

Crossrefs

Cf. A328151, A374090.

Cf. A374089, A374095.

Formula

a(2*n) = A374095(n).

a(n) <= 5*11^(n-1) for all n >= 1. - Jason Yuen, Jun 29 2024