A131788 a(n) = a(n-1) + (sum of the terms, from among the first (n-1) terms of the sequence, which are coprime to the n-th Fibonacci number).

1, 2, 3, 6, 18, 22, 74, 173, 350, 627, 1903, 3980, 11139, 29437, 72720, 108312, 337079, 379735, 988163, 1354929, 4458118, 12200929, 32148649, 78234718, 208109020, 546549127, 1108402372, 3055896646, 8105184898, 8151267237, 29457007624

Offset

1,2

Links

Table of n, a(n) for n=1..31.

Example

The 6th Fibonacci number is 8. Of the first 5 terms, only terms a(1)=1 and a(3)=3 are coprime to 8. So a(6) = a(5) + 1 + 3 = 22.

Maple

with(combinat): a[1] := 1: for n from 2 to 30 do s := 0: for j to n-1 do if gcd(a[j], fibonacci(n)) = 1 then s := s+a[j] else s := s end if end do: a[n] := a[n-1]+s end do: seq(a[n], n = 1 .. 30); # Emeric Deutsch, Jul 17 2007

Crossrefs

Cf. A131787.

Sequence in context: A003183 A213616 A359180 * A294455 A277703 A080338

Adjacent sequences: A131785 A131786 A131787 * A131789 A131790 A131791

Keyword

nonn

Author

Leroy Quet, Jul 15 2007

Extensions

More terms from Emeric Deutsch and Joshua Zucker, Jul 17 2007

Status

approved