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 A100686 a(1) = 1, a(2) = 2; thereafter a(2n+1) = |a(2n)^2-a(2n-1)^2|, a(2n+2) = 2*a(2n-1)*a(2n). 1

%I

%S 1,2,3,4,7,24,527,336,164833,354144,98248054847,116749235904,

%T 3977703802948722503807,22940770664883067253376,

%U 510456831154766758152181998159655209453904127,182503181432559739767250904458105698387204864

%N a(1) = 1, a(2) = 2; thereafter a(2n+1) = |a(2n)^2-a(2n-1)^2|, a(2n+2) = 2*a(2n-1)*a(2n).

%C s = 1 and t = 2 are the initial seed numbers; they give the first Pythagorean pair x = 3, y = 4. Then take s = x, t = y for next seed numbers; these give the next Pythagorean pair x = |s^2-t^2|, y = 2st. Then take s = x, t = y and so on.

%H Planet Math, <a href="https://planetmath.org/pythagoreantriplet">Pythagorean Triplet</a>

%e a(9) = 527^2-336^2 = 164833 because a(7) = 527 and a(8) = 336.

%K nonn,easy

%O 1,2

%A _Pahikkala Jussi_, Dec 08 2004

%E Edited by _N. J. A. Sloane_, Sep 06 2008

%E Defined a(2n+1) by absolute values, added 4 values - _R. J. Mathar_, Oct 14 2010

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Last modified January 18 11:57 EST 2022. Contains 350455 sequences. (Running on oeis4.)