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Smallest a(n)>a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, a(1)=7.
1

%I #6 May 29 2015 15:33:23

%S 7,24,32,60,63,84,112,180,189,252,275,660,693,924,1232,1326,1768,1974,

%T 2632,4026,5368,6405,8200,8319,11092,11715,15620,16401,19720,20706,

%U 20880,20910,24752,24960,25300,26565,29716,29835,33048,35055,41496

%N Smallest a(n)>a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, a(1)=7.

%C The sequence is infinite.

%t nxt[n_]:= Module[{k = n + 1}, While[!IntegerQ[Sqrt[n^2 + k^2]], k++]; k]; NestList[nxt,7,40] (* _Harvey P. Dale_, May 29 2015 *)

%Y Cf. A076600.

%K nonn

%O 1,1

%A _Zak Seidov_, Oct 25 2002