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A126870 a(1)=1. a(n) = number of earlier terms of the sequence which are coprime to the sum of distinct prime divisors of n. 0
1, 1, 2, 2, 4, 5, 6, 3, 6, 9, 10, 9, 12, 7, 7, 8, 16, 15, 18, 17, 8, 21, 22, 20, 20, 12, 16, 17, 28, 10, 30, 12, 9, 33, 7, 28, 36, 17, 16, 33, 40, 9, 42, 43, 19, 37, 46, 39, 41, 42, 21, 24, 52, 45, 25, 32, 24, 57, 58, 23, 60, 34, 24, 28, 15, 29, 66, 65, 29, 27, 70, 57, 72, 39, 35 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..75.

EXAMPLE

The sum of the distinct prime divisors of 12 is 2+3 = 5. So a(12) is the number of terms from among (a(1),a(2),...a(11)) which are coprime to 5. There are 9 such terms, so a(12) = 9.

MATHEMATICA

g[l_List] := Block[{n = Length[l] + 1}, Append[l, Count[GCD[l, f[n]], 1]]]; Nest[g, {1}, 75] (* Ray Chandler, Mar 26 2007 *)

CROSSREFS

Cf. A008472.

Sequence in context: A049269 A085085 A121600 * A137413 A010848 A133937

Adjacent sequences:  A126867 A126868 A126869 * A126871 A126872 A126873

KEYWORD

nonn

AUTHOR

Leroy Quet, Mar 16 2007

EXTENSIONS

Extended by Ray Chandler, Mar 26 2007

STATUS

approved

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Last modified May 7 10:17 EDT 2021. Contains 343649 sequences. (Running on oeis4.)