A124406 For n >= 2, n = Sum_{n/2<=k<=n, gcd(k,n)=1} a(k).

2, 3, 4, 1, 6, 0, 2, 1, 8, 0, 10, -8, -4, 8, 2, 1, 12, -2, 2, 0, 10, 2, 14, -18, -14, 2, 12, 6, 2, 2, -6, 15, 14, -2, 38, -42, -32, 16, 26, -4, 78, -66, -74, 26, 2, 66, 56, -94, -26, -112, -12, 164, 18, -38, -16, -134, -8, 204, 46, -42, -48, -338, 2, 453, 10, -50, -4, -252, 24, 272, 64, -104, -64, -176, -6, 242, 48, -28, -20, -402

Offset

1,1

Links

Table of n, a(n) for n=1..80.

Example

The integers which are >= 9/2 and are < 9 and are coprime to 9 are 5,7,8. So a(5) + a(7) + a(8) = 9.

Mathematica

f[n_] := Select[Range[Ceiling[n/2], n], GCD[ #, n] == 1 &]; g[l_] := Block[{n = Length[l] + 2}, Append[l, n - Plus @@ l[[Most[f[n]]]]]]; Nest[g, {}, 80] (* Ray Chandler, Nov 13 2006 *)

Crossrefs

Cf. A124407.

Sequence in context: A117386 A101174 A050144 * A225650 A340087 A239223

Adjacent sequences: A124403 A124404 A124405 * A124407 A124408 A124409

Keyword

sign

Author

Leroy Quet, Oct 31 2006

Extensions

Extended by Ray Chandler, Nov 13 2006

Status

approved