A072585 Numbers k such that k and phi(k) end with the same digit in base 10.

1, 38, 42, 50, 58, 76, 84, 100, 102, 110, 116, 118, 126, 150, 152, 158, 168, 178, 182, 200, 204, 218, 220, 222, 232, 236, 250, 252, 278, 282, 294, 298, 300, 304, 306, 310, 316, 322, 330, 336, 350, 356, 358, 364, 378, 398, 400, 402, 408, 410, 436, 440, 442

Offset

1,2

Comments

Numbers k such that the cototient of k is divisible by 10. - Darío Clavijo, Apr 04 2023

Links

Table of n, a(n) for n=1..53.

Formula

Probably lim n -> infinity a(n)/n = 10.

Prog

(PARI) isok(n) = (n % 10) == (eulerphi(n) % 10); \\ Michel Marcus, Nov 26 2013
(Python)
from sympy import totient
isok = lambda n: (n-totient(n))%10==0 # Darío Clavijo, Apr 04 2023

Crossrefs

Cf. A000010, A051953.

Sequence in context: A350854 A272035 A056027 * A050874 A144798 A066473

Adjacent sequences: A072582 A072583 A072584 * A072586 A072587 A072588

Keyword

base,nonn

Author

Benoit Cloitre, Aug 06 2002

Status

approved