A123338 a(0) = a(1) = 1. For n >= 2, a(n) = largest divisor of (a(n-1) + a(n-2)) which is coprime to n.

1, 1, 1, 2, 3, 1, 1, 2, 3, 5, 1, 6, 7, 1, 1, 2, 3, 5, 1, 6, 7, 13, 5, 18, 23, 41, 1, 14, 15, 1, 1, 2, 3, 5, 1, 6, 7, 13, 5, 2, 7, 9, 1, 10, 1, 11, 3, 14, 17, 31, 3, 2, 5, 7, 1, 8, 9, 17, 13, 30, 43, 73, 29, 34, 63, 97, 5, 102, 107, 209, 79, 288, 367, 655, 511, 1166, 1677, 2843, 565, 3408

Offset

0,4

Links

G. C. Greubel, Table of n, a(n) for n = 0..1000

Example

a(20)+a(21) = 20. The largest divisor of 20 which is coprime to 22 is 5. So a(22) = 5.

Mathematica

t[n_, m_] := Last[Select[Divisors[m], GCD[ #, n] == 1 &]]; f[l_List] := Append[l, t[Length[l], l[[ -1]] + l[[ -2]]]]; Nest[f, {1, 1}, 80] (* Ray Chandler, Oct 17 2006 *)

Crossrefs

Sequence in context: A111879 A193280 A114732 * A152735 A249128 A299481

Adjacent sequences: A123335 A123336 A123337 * A123339 A123340 A123341

Keyword

nonn

Author

Leroy Quet, Oct 11 2006

Extensions

Extended by Ray Chandler, Oct 17 2006

Status

approved