A125843 a(1)=1. a(n) = the sum of the 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, 5, 3, 7, 3, 10, 9, 7, 12, 16, 8, 21, 15, 12, 27, 31, 15, 29, 30, 29, 32, 53, 17, 60, 46, 36, 46, 59, 22, 96, 67, 60, 62, 132, 8, 144, 109, 45, 140, 202, 53, 182, 149, 120, 184, 276, 111, 230, 178, 181, 208, 390, 176, 407, 252, 237, 283, 378, 181

Offset

1,4

Links

Table of n, a(n) for n=1..66.

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) = 1+1+1+2+2 = 7.

Mathematica

f[l_List] := Block[{n = Length[l] + 1}, Append[l, Plus @@ Select[Take[l, Floor[n/2]], GCD[ #, n] == 1 &]]]; Nest[f, {1}, 65] (* Ray Chandler, Dec 11 2006 *)

Crossrefs

Cf. A125842.

Sequence in context: A301498 A136132 A136545 * A210957 A306246 A147665

Adjacent sequences: A125840 A125841 A125842 * A125844 A125845 A125846

Keyword

nonn

Author

Leroy Quet, Dec 10 2006

Extensions

Extended by Ray Chandler, Dec 11 2006

Status

approved