A157605 a(2)=1. a(n) = the largest integer coprime to a(n-1) and less than the n-th Fibonacci number.

1, 1, 2, 3, 7, 12, 19, 33, 53, 88, 141, 232, 375, 608, 985, 1596, 2581, 4180, 6763, 10945, 17709, 28655, 46367, 75024, 121391, 196417, 317809, 514228, 832037, 1346268, 2178307, 3524577, 5702885, 9227464, 14930349, 24157816, 39088167, 63245984

Offset

2,3

Links

Robert Israel, Table of n, a(n) for n = 2..4762

Maple

f:= proc(n) option remember;
     local k;
     for k from combinat:-fibonacci(n)-1 by -1 do
       if igcd(k, procname(n-1)) = 1 then return k fi
     od
   end proc:
f(2):= 1:
map(f, [$2..40]); # Robert Israel, Nov 09 2025

Mathematica

a[n_] := a[n] = Block[{k = Fibonacci@n - 1}, While[ GCD[k, a[n - 1]] > 1, k-- ]; k]; a[1] = a[2] = 1; Table[ a[n], {n, 2, 40}] (* Robert G. Wilson v, May 04 2009 *)

Crossrefs

Cf. A157420, A157604, A157606.

Sequence in context: A121430 A217379 A023606 * A056179 A222196 A184696

Adjacent sequences: A157602 A157603 A157604 * A157606 A157607 A157608

Keyword

nonn

Author

Leroy Quet, Mar 02 2009

Extensions

More terms from Robert G. Wilson v, May 04 2009

Status

approved