A130043 a(1)=1. a(n) = number of earlier terms which are coprime to the largest odd divisor of n.

1, 1, 2, 3, 4, 4, 6, 7, 6, 9, 10, 7, 12, 11, 8, 15, 16, 11, 18, 17, 11, 18, 22, 15, 21, 25, 16, 24, 28, 16, 30, 31, 16, 32, 25, 23, 36, 37, 25, 32, 40, 25, 42, 39, 23, 43, 46, 32, 43, 40, 34, 50, 52, 38, 39, 50, 39, 57, 58, 32, 60, 60, 39, 63, 45, 38, 66, 65, 41, 47, 70, 47, 72

Offset

1,3

Links

Table of n, a(n) for n=1..73.

Example

The largest odd divisor of 12 is 3. So a(12) is the number of terms from among (a(1),a(2),...a(11)) which are coprime to 3, which is 7.

Maple

lod:=proc(n) if n mod 2 = 1 then n else lod(n/2) fi end: seq(lod(n), n=1..100): a[1]:=1: for n from 2 to 100 do a[n]:=0: for j from 1 to n-1 do if igcd(a[j], lod(n))=1 then a[n]:=1+a[n] else fi od: od: seq(a[n], n=1..100); # lod finds the largest odd divisor - Emeric Deutsch, May 22 2007

Crossrefs

Cf. A130044, A000265.

Sequence in context: A072455 A177862 A066981 * A089266 A178993 A193768

Adjacent sequences: A130040 A130041 A130042 * A130044 A130045 A130046

Keyword

nonn

Author

Leroy Quet, May 02 2007

Extensions

More terms from Emeric Deutsch, May 22 2007

Status

approved