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 A076601 a(1)=3, a(n_even)=(a(n-1)^2-1)/2; a(n_odd)=a(n-1)+1. 1

%I

%S 3,4,5,12,13,84,85,3612,3613,6526884,6526885,21300113901612,

%T 21300113901613,226847426110843688722000884,

%U 226847426110843688722000885,25729877366557343481074291996721923093306518970391612,25729877366557343481074291996721923093306518970391613

%N a(1)=3, a(n_even)=(a(n-1)^2-1)/2; a(n_odd)=a(n-1)+1.

%C {3, 4, 5}, {5, 12, 13}, {13, 84, 85}... are sides {a<b<c} of the right triangles, with hypotenuse c=b+1.

%t Transpose[NestList[{#[[1]]+1,If[EvenQ[#[[1]]+1],(#[[2]]^2-1)/2,#[[2]]+1]}&,{1,3},20]][[2]] (* _Harvey P. Dale_, May 02 2012 *)

%K easy,nonn

%O 1,1

%A _Zak Seidov_, Oct 21 2002

%E More terms from _Harvey P. Dale_, May 02 2012

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Last modified January 26 07:38 EST 2022. Contains 350577 sequences. (Running on oeis4.)