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A076603 a(1)=9, a(n_even)=(a(n-1)^2-1)/2; a(n_odd)=a(n-1)+1. 1
9, 40, 41, 840, 841, 353640, 353641, 62530978440, 62530978441, 1955061632394403395240, 1955061632394403395241, 1911132993230334657643987512400814230724040, 1911132993230334657643987512400814230724041 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..13.

MATHEMATICA

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 *)

CROSSREFS

Sequence in context: A173764 A331343 A002085 * A346336 A003354 A063164

Adjacent sequences:  A076600 A076601 A076602 * A076604 A076605 A076606

KEYWORD

easy,nonn

AUTHOR

Zak Seidov, Oct 21 2002

EXTENSIONS

More terms from Harvey P. Dale, Oct 15 2012

STATUS

approved

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Last modified January 17 22:33 EST 2022. Contains 350410 sequences. (Running on oeis4.)