A343912 a(n) = n - phi(n - phi(n)), where phi is the Euler totient function.

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

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