A125296 a(1)=1. a(n) is the number of earlier terms of the sequence which are noncomposites (1 or primes) and are coprime to n.

1, 1, 2, 2, 4, 2, 5, 3, 6, 3, 8, 3, 9, 6, 5, 7, 11, 6, 12, 7, 8, 9, 13, 8, 12, 10, 11, 10, 15, 7, 16, 13, 12, 14, 12, 11, 18, 15, 13, 14, 19, 11, 21, 14, 16, 18, 21, 15, 18, 16, 18, 15, 21, 15, 15, 15, 17, 19, 23, 16, 24, 21, 18, 21, 19, 15, 25, 21, 21, 17, 26, 20, 26, 23, 22, 21, 20

Offset

1,3

Links

Table of n, a(n) for n=1..77.

Example

The noncomposites among the first 7 terms of the sequence are 1,1,2,2,2,5. Of these, three terms (1,1,5) are coprime to 8. So a(8)=3.

Mathematica

f[l_List] := Append[l, Length[Select[l, GCD[ #, Length[l] + 1] == 1 && (PrimeQ[ # ] || # == 1) &]]]; Nest[f, {1}, 80] (* Ray Chandler, Dec 11 2006 *)

Crossrefs

Sequence in context: A300837 A321443 A333836 * A366707 A366708 A294097

Adjacent sequences: A125293 A125294 A125295 * A125297 A125298 A125299

Keyword

nonn

Author

Leroy Quet, Dec 08 2006

Extensions

Extended by Ray Chandler, Dec 11 2006

Status

approved