A125842 a(1)=1. a(n) = the number of terms from among the first floor(n/2) terms of the sequence which are coprime to n.

1, 1, 1, 2, 2, 3, 3, 3, 4, 3, 5, 3, 6, 5, 5, 6, 8, 3, 9, 7, 6, 8, 11, 4, 11, 9, 7, 10, 14, 3, 15, 11, 9, 11, 14, 6, 18, 13, 10, 11, 20, 6, 21, 14, 9, 15, 23, 8, 23, 13, 15, 17, 26, 10, 22, 16, 17, 18, 29, 7, 30, 20, 15, 21, 27, 8, 33, 23, 20, 17, 35, 12, 36, 23, 17, 24, 30, 12, 39, 21, 24

Offset

1,4

Links

Table of n, a(n) for n=1..81.

Example

The first floor(15/2) terms of the sequence are 1,1,1,2,2,3,3. Of these, five terms (1,1,1,2,2) are coprime to 15. So a(15) = 5.

Mathematica

f[l_List] := Block[{n = Length[l] + 1}, Append[l, Length[Select[Take[l, Floor[n/2]], GCD[ #, n] == 1 &]]]]; Nest[f, {1}, 80] (* Ray Chandler, Dec 11 2006 *)

Crossrefs

Cf. A125843.

Sequence in context: A230022 A049846 A086712 * A029865 A211190 A072644

Adjacent sequences: A125839 A125840 A125841 * A125843 A125844 A125845

Keyword

nonn

Author

Leroy Quet, Dec 10 2006

Extensions

Extended by Ray Chandler, Dec 11 2006

Status

approved