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A326194
Number of iterations of x -> A009194(x) needed to reach a fixed point when starting from x = n, where A009194(x) = gcd(x, sigma(x)).
7
0, 1, 1, 1, 1, 0, 1, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 1, 0, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 3, 1, 1, 1, 2, 2, 2, 1, 2, 1, 1, 2, 2, 1, 1, 1, 2, 1, 2, 1, 3, 1, 2, 1, 1, 1, 1, 1, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 2, 2, 1, 3, 2, 2, 1, 2, 2, 3, 1, 1, 2, 1, 1, 1, 1, 2, 2
OFFSET
1,10
LINKS
FORMULA
If gcd(n,sigma(n)) = n, then a(n) = 0, otherwise a(n) = 1 + a(gcd(n,sigma(n))).
a(n) < A326196(n).
PROG
(PARI) A326194(n) = { my(u=gcd(n, sigma(n))); if(u==n, 0, 1+A326194(u)); };
CROSSREFS
Cf. A000203, A007691 (positions of zeros), A009194, A326195, A326196.
Sequence in context: A306717 A195969 A023518 * A331251 A309858 A375508
KEYWORD
nonn
AUTHOR
Antti Karttunen, Aug 24 2019
STATUS
approved