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A116204 a(0) = 1; for n >= 1, a(n) = the number of positive divisors of n which are coprime to a(n-1). 2
1, 1, 2, 2, 1, 2, 2, 2, 1, 3, 4, 2, 2, 2, 2, 4, 1, 2, 3, 2, 2, 4, 2, 2, 2, 3, 4, 4, 2, 2, 4, 2, 1, 4, 2, 4, 3, 2, 2, 4, 2, 2, 4, 2, 2, 6, 2, 2, 2, 3, 6, 2, 2, 2, 4, 4, 2, 4, 2, 2, 4, 2, 2, 6, 1, 4, 4, 2, 2, 4, 4, 2, 3, 2, 2, 6, 2, 4, 4, 2, 2, 5, 4, 2, 4, 4, 2, 4, 2, 2, 6, 4, 2, 4, 2, 4, 2, 2, 3, 2, 3, 2, 4, 2, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..104.

EXAMPLE

a(11) = 2. There are 2 positive divisors (1 and 3) of 12 which are coprime to 2. So a(12) = 2.

MAPLE

with(numtheory): a[0]:=1: for n from 1 to 140 do ct:=0: div:=divisors(n): for j from 1 to tau(n) do if igcd(div[j], a[n-1])=1 then ct:=ct+1 else ct:=ct: fi: od: a[n]:=ct: od: seq(a[n], n=0..140); # Emeric Deutsch, Apr 27 2007

A116204 := proc(nmax) local a, n, dvs, resl, d ; a := [1] ; while nops(a) < nmax do n := nops(a) ; dvs := numtheory[divisors](n) ; resl :=0 ; for d from 1 to nops(dvs) do if gcd(op(d, dvs), op(-1, a)) = 1 then resl := resl+1 ; fi ; od ; a := [op(a), resl] ; od ; RETURN(a) ; end: A116204(100) ; # R. J. Mathar, Apr 27 2007

CROSSREFS

Sequence in context: A107260 A279346 A168258 * A291592 A159905 A283735

Adjacent sequences:  A116201 A116202 A116203 * A116205 A116206 A116207

KEYWORD

nonn

AUTHOR

Leroy Quet, Apr 16 2007

EXTENSIONS

More terms from R. J. Mathar and Emeric Deutsch, Apr 27 2007

STATUS

approved

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Last modified September 15 20:11 EDT 2019. Contains 327086 sequences. (Running on oeis4.)