A076672 Smallest a(n)>a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, a(1)=6.

6, 8, 15, 20, 21, 28, 45, 60, 63, 84, 112, 180, 189, 252, 275, 660, 693, 924, 1232, 1326, 1768, 1974, 2632, 4026, 5368, 6405, 8200, 8319, 11092, 11715, 15620, 16401, 19720, 20706, 20880, 20910, 24752, 24960, 25300, 26565, 29716

Offset: 1

Author

Zak Seidov, Oct 25 2002

Keywords

• nonn

Comments

The sequence is infinite.

Crossrefs

Cf. A076600, A076671 (starting at 5).

Programs

Mathematica

Clear[nxt]; nxt[n_]:=Module[{i=n+1},While[!IntegerQ[Sqrt[n^2+i^2]],i++]; i]; NestList[nxt,6,40] (* Harvey P. Dale, Dec 03 2010 *)