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A124693 a(1)=1. a(n+1) = sum a(k), where the sum is over all positive integers k, k <= n, where each positive integer <= k and coprime to k is also coprime to n. 0
1, 1, 2, 4, 6, 14, 16, 44, 64, 82, 88, 322, 338, 982, 1002, 1006, 2456, 6428, 6766, 19622, 19710, 19728, 19874, 98556, 105322, 126042, 126510, 252610, 253612, 1061208, 1061210, 3183626, 4770276, 4770358, 4772814, 4772828, 5939358, 31392886 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..38.

EXAMPLE

The positive integers k, where k <= 6 and where each positive integer <= k and coprime to k is also coprime to 6, are 1,2,6. So a(7) = a(1)+a(2)+a(6) = 1+1+14 = 16.

MATHEMATICA

f[n_] := Select[ Range[n], GCD[ #, n] == 1 &]; g[n_] := Select[ Range[n], Times @@ GCD[f[ # ], n] == 1 &]; h[l_List] := Append[l, Plus @@ l[[g[Length[l]]]]]; Nest[h, {1}, 38] (*Chandler*)

CROSSREFS

Cf. A126260.

Sequence in context: A282139 A138307 A323101 * A095698 A277909 A064409

Adjacent sequences:  A124690 A124691 A124692 * A124694 A124695 A124696

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 25 2006

EXTENSIONS

Extended by Ray Chandler, Dec 26 2006

STATUS

approved

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Last modified February 21 06:40 EST 2019. Contains 320371 sequences. (Running on oeis4.)