%I A116204
%S A116204 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,
%T A116204 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,
%U A116204 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
%N A116204 a(0) = 1; for n>=1, a(n) = the number of positive divisors of n which 
               are coprime to a(n-1).
%H A116204 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A116204 a(11) = 2. There are 2 positive divisors (1 and 3) of 12 which are coprime 
               to 2. So a(12) = 2.
%p A116204 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); (Deutsch)
%p A116204 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) ; (Mathar)
%Y A116204 Sequence in context: A037196 A116543 A107260 this_sequence A159905 A106054 
               A160242
%Y A116204 Adjacent sequences: A116201 A116202 A116203 this_sequence A116205 A116206 
               A116207
%K A116204 nonn
%O A116204 0,3
%A A116204 Leroy Quet Apr 16 2007
%E A116204 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Emeric 
               Deutsch (deutsch(AT)duke.poly.edu), Apr 27 2007