Numbers k such that (k, sigma(k)) lies on a circle with integral radius centered at the origin, i.e., k^2 + sigma(k)^2 is a square.

A066764

Numbers k such that (k, sigma(k)) lies on a circle with integral radius centered at the origin, i.e., k^2 + sigma(k)^2 is a square.

Terms

    a(0) =3a(1) =8a(2) =30a(3) =140a(4) =315a(5) =319a(6) =460a(7) =840a(8) =864a(9) =936a(10) =1040a(11) =1287a(12) =1836a(13) =2480a(14) =2600a(15) =6076a(16) =6200a(17) =7788a(18) =11398a(19) =12035a(20) =12415a(21) =12584a(22) =13260a(23) =13734a(24) =15886a(25) =18480a(26) =26078a(27) =33820a(28) =40640a(29) =42665

External references