A124407 - OEIS

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A124407

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

1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, -1, -1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, -2, -2, 0, 1, 1, -1, 1, 0, 1, 1, 0, 3, -4, -3, 1, 1, 1, 6, -5, -5, 0, 0, 6, 3, -6, -2, -10, -2, 13, 0, -3, 1, -12, -2, 17, 2, -1, -2, -30, 0, 41, -1, -6, 0, -22, 3, 22, 2, -6, -3, -14, -2, 15, -1, 4, 2, -27, 8, 24, 2, -49, -7, -1, 0, 45, -2, -24, 5, -89, 0, 83, 5, 25, -3, -9, -8, 8

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,24

LINKS

Table of n, a(n) for n=1..100.

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) = 1.

MATHEMATICA

f[n_] := Select[Range[Ceiling[n/2], n], GCD[ #, n] == 1 &]; g[l_] :=Append[l, 1 - Plus @@ l[[Most[f[Length[l] + 2]]]]]; Nest[g, {}, 100] (* Ray Chandler, Nov 13 2006 *)

CROSSREFS

Cf. A124406.

Sequence in context: A076898 A174294 A089385 * A294624 A290531 A376629

Adjacent sequences: A124404 A124405 A124406 * A124408 A124409 A124410

KEYWORD

sign

AUTHOR

Leroy Quet, Oct 31 2006

EXTENSIONS

Extended by Ray Chandler, Nov 13 2006

STATUS

approved