OFFSET
1,2
COMMENTS
First differs from A055874 at a(20).
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = 1 + A129308(n).
a(2n-1) = 1; a(2n) = 1 + A007862(n).
Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 2. - Amiram Eldar, Dec 31 2023
MAPLE
with(numtheory):
a:= n-> add(`if`(d=1 or irem(n, d-1)=0, 1, 0), d=divisors(n)):
seq(a(n), n=1..200); # Alois P. Heinz, Oct 17 2011
MATHEMATICA
d1[n_]:=Module[{d=Rest[Divisors[n]]}, Count[d, _?(Divisible[n, #-1]&)]+1]; Array[d1, 90] (* Harvey P. Dale, Oct 31 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Sep 19 2011
STATUS
approved