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A343912 a(n) = n - phi(n - phi(n)), where phi is the Euler totient function. 0
1, 1, 2, 3, 4, 4, 6, 6, 7, 8, 10, 8, 12, 10, 9, 12, 16, 14, 18, 16, 15, 18, 22, 16, 21, 20, 21, 20, 28, 20, 30, 24, 21, 28, 25, 28, 36, 30, 31, 32, 40, 34, 42, 36, 33, 38, 46, 32, 43, 42, 33, 40, 52, 42, 47, 40, 45, 50, 58, 40, 60, 46, 45, 48, 49, 44, 66, 56, 49, 48, 70, 56, 72 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

If p is prime, a(p) = p - phi(p - phi(p)) = p - phi(1) = p - 1. - Wesley Ivan Hurt, May 21 2021

LINKS

Table of n, a(n) for n=1..73.

FORMULA

a(n) = n - A000010(A051953(n)).

MATHEMATICA

Table[n - EulerPhi[n - EulerPhi[n]], {n, 100}]

CROSSREFS

Cf. A000010 (phi), A051953 (cototient).

Sequence in context: A061984 A337125 A063208 * A262265 A227683 A321166

Adjacent sequences:  A343909 A343910 A343911 * A343913 A343914 A343915

KEYWORD

nonn

AUTHOR

Wesley Ivan Hurt, May 03 2021

STATUS

approved

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Last modified July 27 15:29 EDT 2021. Contains 346307 sequences. (Running on oeis4.)