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A347879
The nearest common ancestor of n and sigma(n) in the Doudna tree (A005940).
7
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.
FORMULA
a(n) = A348041(n, A000203(n)).
PROG
(PARI) A347879(n) = A348041sq(n, sigma(n)); \\ Needs also code from A348041.
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 13 2021
STATUS
approved