A128330 a(1)=1. a(n) = number of positive numbers <= n that are coprime to the product of the first n-1 terms of this sequence.

1, 2, 2, 2, 3, 2, 3, 3, 3, 3, 4, 4, 5, 4, 4, 4, 5, 5, 6, 6, 6, 6, 7, 6, 6, 6, 6, 6, 7, 7, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 11, 10, 10, 10, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 16, 16, 16, 16, 16, 16, 17, 16, 16, 16, 17

Offset: 1

Author

Leroy Quet, May 04 2007

Keywords

• nonn

Examples

			The first 6 terms of the sequence are 1,2,2,2,3,2,3. The number of positive integers <= 7 that are coprime to 1, 2 and 3 is three, these integers being 1, 5 and 7. So a(7) = 3.
		

Programs

Maple

a[1]:=1: for n from 2 to 105 do a[n]:=0: for j from 1 to n do if igcd(j,product(a[i],i=1..n-1))=1 then a[n]:=a[n]+1 else fi od: od: seq(a[n],n=1..105); # Emeric Deutsch, May 22 2007

Extensions

More terms from Emeric Deutsch, May 22 2007