A129456 a(0)=1. a(n) is the number of earlier terms of the sequence that are coprime to (n+a(n-1)).

1, 1, 2, 3, 4, 4, 3, 4, 2, 9, 10, 8, 5, 3, 14, 15, 16, 12, 2, 12, 8, 21, 22, 13, 24, 23, 24, 17, 16, 17, 30, 31, 20, 33, 34, 22, 15, 15, 38, 34, 17, 18, 8, 23, 44, 45, 43, 10, 21, 15, 39, 10, 23, 25, 54, 55, 36, 35, 36, 44, 26, 39, 62, 49, 64, 41, 66, 61, 43, 29, 41, 31, 72, 58, 21

Offset

0,3

Links

Table of n, a(n) for n=0..74.

Example

11 + a(10) = 21. There are 8 terms among a(0), a(1), ..., a(10) that are coprime to 21. (These terms are a(0), a(1), a(2), a(4), a(5), a(7), a(8) and a(10).) So a(11) = 8.

Maple

a[0]:=1: for n from 1 to 120 do ct:=0: for i from 0 to n-1 do if igcd(a[i], n+a[n-1])=1 then ct:=ct+1 else ct:=ct: fi: od: a[n]:=ct: od: seq(a[n], n=0..100); # Emeric Deutsch, May 05 2007

Crossrefs

Cf. A129457.

Sequence in context: A107898 A128863 A117391 * A030412 A329526 A160371

Adjacent sequences: A129453 A129454 A129455 * A129457 A129458 A129459

Keyword

nonn

Author

Leroy Quet, Apr 16 2007

Extensions

More terms from Emeric Deutsch, May 05 2007

Status

approved