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.

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

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 * A364049 A368866 A137413

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