A076601 - OEIS

A076601

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

3, 4, 5, 12, 13, 84, 85, 3612, 3613, 6526884, 6526885, 21300113901612, 21300113901613, 226847426110843688722000884, 226847426110843688722000885, 25729877366557343481074291996721923093306518970391612, 25729877366557343481074291996721923093306518970391613

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OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..17.

MATHEMATICA

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

CROSSREFS

Sequence in context: A109350 A239356 A077034 * A372590 A242669 A090829

Adjacent sequences: A076598 A076599 A076600 * A076602 A076603 A076604