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

1,2

Links

Table of n, a(n) for n=1..83.

Example

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.

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

Crossrefs

Sequence in context: A299230 A182576 A368869 * A133801 A372433 A181630

Adjacent sequences: A128327 A128328 A128329 * A128331 A128332 A128333

Keyword

nonn

Author

Leroy Quet, May 04 2007

Extensions

More terms from Emeric Deutsch, May 22 2007

Status

approved