|
| |
|
|
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; internal format)
|
|
|
|
OFFSET
| 0,3
|
|
|
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); (Deutsch)
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)
|
|
|
CROSSREFS
| Sequence in context: A116543 A107260 A168258 * A159905 A106054 A169695
Adjacent sequences: A116201 A116202 A116203 * A116205 A116206 A116207
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Leroy Quet Apr 16 2007
|
|
|
EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 27 2007
|
| |
|
|
