A347879 The nearest common ancestor of n and sigma(n) in the Doudna tree (A005940).

1, 2, 2, 2, 3, 6, 2, 2, 2, 2, 3, 3, 7, 3, 6, 2, 2, 2, 5, 10, 2, 2, 3, 6, 2, 5, 2, 28, 3, 2, 2, 2, 3, 2, 6, 2, 19, 3, 7, 3, 5, 3, 11, 5, 3, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 3, 5, 3, 3, 3, 31, 3, 5, 2, 5, 2, 17, 5, 3, 2, 2, 2, 37, 17, 2, 3, 6, 5, 5, 5, 4, 5, 5, 5, 2, 7, 3, 3, 3, 3, 5, 5, 2, 2, 3, 3, 2, 2, 7, 2, 13, 2

Offset

1,2

Comments

The fixed points of this sequence is given by the union of {2} and A336702.

The positions x such that a(x) = A252463(x) is given by the union of {1} and A347391.

The positions x such that a(x) = A252463(A252463(x)) is given by the union of {1} and A347392.

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Index entries for sequences computed from indices in prime factorization

Index entries for sequences related to sigma(n)

Formula

a(n) = A348041(n, A000203(n)).

Prog

(PARI) A347879(n) = A348041sq(n, sigma(n)); \\ Needs also code from A348041.

Crossrefs

Cf. A000203, A005940, A252463, A332221, A336702, A347381, A347391, A347392, A348040, A348041.

Sequence in context: A022867 A268595 A299019 * A070610 A156820 A104346

Adjacent sequences: A347876 A347877 A347878 * A347880 A347881 A347882

Keyword

nonn

Author

Antti Karttunen, Oct 13 2021

Status

approved