A131787 a(n) = a(n-1) + (number of terms, from among the first (n-1) terms of the sequence, which are coprime to the n-th Fibonacci number).

1, 2, 3, 5, 8, 11, 17, 23, 28, 35, 45, 51, 63, 76, 83, 92, 108, 117, 135, 144, 156, 177, 199, 205, 224, 249, 264, 279, 307, 319, 349, 364, 385, 418, 443, 456, 492, 529, 553, 566, 606, 629, 671, 696, 713, 758, 804, 817, 862, 899, 929, 962, 1014, 1041, 1089, 1114

Offset

1,2

Links

Table of n, a(n) for n=1..56.

Example

The 6th Fibonacci number is 8. Of the first 5 terms, only terms a(1)=1, a(3)=3 and a(4) = 5 are coprime to 8. Since there are 3 such terms, a(6) = a(5) + 3 = 11.

Maple

with(combinat): a[1]:= 1: for n from 2 to 55 do ct := 0: for j to n-1 do if gcd(a[j], fibonacci(n)) = 1 then ct := ct+1 else ct := ct end if end do: a[n]:= a[n-1]+ct end do: seq(a[n], n = 1 .. 55); # Emeric Deutsch, Jul 24 2007

Crossrefs

Cf. A131788.

Sequence in context: A039847 A046938 A060677 * A091498 A227562 A370729

Adjacent sequences: A131784 A131785 A131786 * A131788 A131789 A131790

Keyword

nonn

Author

Leroy Quet, Jul 15 2007

Extensions

More terms from Joshua Zucker and Emeric Deutsch, Jul 18 2007

Status

approved