OFFSET
1,1
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
KEYWORD
sign
AUTHOR
Leroy Quet, Oct 31 2006
EXTENSIONS
Extended by Ray Chandler, Nov 13 2006
STATUS
approved