OFFSET
1,2
COMMENTS
Number of distinct vertices in the directed acyclic graph formed by edge relations x -> A009194(x) and x -> A009195(x), where n is the unique root of the graph.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
EXAMPLE
From n = 12 we can reach any of the following of its 6 divisors: 12 (with an empty combination of transitions), 4 (as A009194(12) = A009195(12) = 4), 2 (as A009195(4) = 2) and 1 (as A009194(4) = 1 = A009194(2) = A009195(2)), thus a(12) = 4.
The directed acyclic graph formed from those two transitions with 12 as its unique root looks like this:
12
|
4
| \
| 2
| /
1
PROG
(PARI)
A326196aux(n, xs) = { xs = setunion([n], xs); if(1==n, xs, my(a=gcd(n, eulerphi(n)), b=gcd(n, sigma(n))); xs = A326196aux(a, xs); if((a==b)||(b==n), xs, A326196aux(b, xs))); };
A326196(n) = length(A326196aux(n, Set([])));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Aug 24 2019
STATUS
approved