A097559 a(n) = number of terms among {a(1), a(2), a(3), ..., a(n-1)} that are coprime to n; a(1)=2.

2, 0, 1, 1, 3, 2, 5, 4, 6, 3, 9, 3, 11, 8, 7, 9, 15, 5, 17, 10, 11, 12, 21, 8, 19, 16, 16, 14, 27, 7, 29, 19, 19, 20, 24, 13, 35, 20, 25, 19, 39, 14, 41, 25, 23, 28, 45, 20, 40, 23, 35, 30, 51, 22, 36, 28, 35, 33, 57, 16, 59, 37, 34, 38, 46, 23, 65, 38, 45, 27, 69, 27, 71, 44, 38, 40

Offset

1,1

Comments

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

Links

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

Example

a(8)=4 because among the first seven terms, namely 2,0,1,1,3,2,5, there are 4 terms that are relatively prime to 8 (1,1,3 and 5).

Maple

a[1]:=2: for n from 2 to 100 do s:=0: for j from 1 to n-1 do if gcd(a[j], n)=1 then s:=s+1 else s:=s fi od: a[n]:=s: od: seq(a[n], n=1..84); # Emeric Deutsch

Mathematica

a[1] = 2; a[n_] := a[n] = Count[ GCD[ Table[ a[i], {i, n - 1}], n], 1]; Array[a, 76] (* Robert G. Wilson v, Dec 27 2005 *)

Crossrefs

Cf. A096216.

Sequence in context: A265336 A219782 A035788 * A293108 A172237 A246181

Adjacent sequences: A097556 A097557 A097558 * A097560 A097561 A097562

Keyword

nonn

Author

Leroy Quet, Aug 27 2004

Extensions

More terms from Emeric Deutsch, Aug 03 2005

Status

approved