A113925 a(1)=0. a(1)=1. a(n+2) = gcd(a(n+1) + a(n), n).

0, 1, 1, 2, 3, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 3, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 3, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 3, 5, 1, 6, 1, 1, 1, 2, 1, 3, 1, 2, 3, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 3, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 3, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 3, 1, 1, 2, 1, 1, 1, 2, 1, 3, 1, 2, 3, 5, 1, 6, 1

Offset

1,4

Comments

a(1)'s value is arbitrary. Replacing a(1) with any integer would not alter the rest of the sequence.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

a(14) = gcd(a(13) + a(12), 12) = gcd(1+2, 12) = gcd(3, 12) = 3.

Maple

a[1]:=0: a[2]:=1: for n from 3 to 135 do a[n]:=gcd(a[n-1]+a[n-2], n-2) od: seq(a[n], n=1..117); # Emeric Deutsch, Feb 07 2006

Mathematica

nxt[{n_, a_, b_}]:={n+1, b, GCD[a+b, n-1]}; NestList[nxt, {2, 0, 1}, 110][[All, 2]] (* Harvey P. Dale, Jun 13 2017 *)

Crossrefs

Sequence in context: A135508 A030413 A139434 * A328231 A180466 A105083

Adjacent sequences: A113922 A113923 A113924 * A113926 A113927 A113928

Keyword

nonn

Author

Leroy Quet, Jan 30 2006

Extensions

More terms from Emeric Deutsch, Feb 07 2006

Status

approved