login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A076603 a(1)=9, a(n_even)=(a(n-1)^2-1)/2; a(n_odd)=a(n-1)+1. 1

%I

%S 9,40,41,840,841,353640,353641,62530978440,62530978441,

%T 1955061632394403395240,1955061632394403395241,

%U 1911132993230334657643987512400814230724040,1911132993230334657643987512400814230724041

%N a(1)=9, a(n_even)=(a(n-1)^2-1)/2; a(n_odd)=a(n-1)+1.

%C {9, 40, 41}, {41, 840, 841}, {841, 353640, 353641}... are sides {a<b<c} of the right triangles, with hypotenuse c=b+1.

%t nxt[{n_,a_}]:={n+1,If[EvenQ[n+1],(a^2-1)/2,a+1]}; Transpose[ NestList[ nxt,{1,9},10]][[2]] (* _Harvey P. Dale_, Oct 15 2012 *)

%K easy,nonn

%O 1,1

%A _Zak Seidov_, Oct 21 2002

%E More terms from _Harvey P. Dale_, Oct 15 2012

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 27 15:52 EDT 2022. Contains 354107 sequences. (Running on oeis4.)