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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS 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: A263799 A299230 A182576 * A133801 A181630 A112310 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 4 04:43 EST 2023. Contains 360046 sequences. (Running on oeis4.)