a(n) = least natural number k such that the distance between (n, sigma(n)) and (n+k, sigma(n+k)) is an integer (i.e., k^2 + (sigma(n+k) - sigma(n))^2 is a square), if such k exists; 0 otherwise.
A066790
a(n) = least natural number k such that the distance between (n, sigma(n)) and (n+k, sigma(n+k)) is an integer (i.e., k^2 + (sigma(n+k) - sigma(n))^2 is a square), if such k exists; 0 otherwise.
Terms
- a(0) =113520a(1) =8a(2) =99585a(3) =44a(4) =5a(5) =5a(6) =48a(7) =10a(8) =280a(9) =3a(10) =45a(11) =3a(12) =2808a(13) =1a(14) =6a(15) =9a(16) =16a(17) =4a(18) =66a(19) =6a(20) =6a(21) =133a(22) =10a(23) =9a(24) =11a(25) =14a(26) =6a(27) =11a(28) =11a(29) =16
External references
- oeis: A066790