A097606 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A097606

a(n) = number of terms among {a(1), a(2), a(3), ..., a(n-1)} that are coprime to n; a(1)=6.

6, 0, 0, 0, 1, 1, 3, 3, 2, 4, 7, 3, 9, 6, 5, 8, 13, 5, 15, 8, 9, 12, 19, 7, 18, 13, 13, 14, 25, 8, 27, 18, 17, 18, 24, 12, 33, 19, 16, 17, 37, 13, 39, 24, 20, 25, 43, 18, 42, 22, 25, 23, 49, 21, 42, 27, 28, 32, 55, 16, 57, 34, 30, 34, 47, 22, 63, 34, 38, 24, 67, 24, 69, 37, 35, 37

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

OFFSET

1,1

COMMENTS

Numbers not present: 10, 11, 29, 31, 36, 41, 48, 51, 54, 58, 62, 65, 68, ...,. - Robert G. Wilson v, Sep 03 2004

LINKS

Table of n, a(n) for n=1..76.

MAPLE

A family of related sequences can be generated using different positive integers for a(1). (a(1)=1 gives sequence A096216.)

MATHEMATICA

a[1] = 6; a[n_] := a[n] = Count[ GCD[n, Table[ a[i], {i, n - 1}]], 1]; Table[ a[n], {n, 76}] (* Robert G. Wilson v, Sep 03 2004 *)

CROSSREFS