A201253 Numbers k such that phi(k+1) = 5*phi(k).

11242770, 18673200, 77805000, 117138840, 122649450, 278023200, 393513120, 881879460, 2177410830, 2364390210, 3440848320, 3919303080, 5151045900, 5836032510, 7284273360, 8029787220, 8505803460, 12998545560, 13081794180, 13759304790, 14031484740, 14104654410

Offset

1,1

Links

Giovanni Resta, Table of n, a(n) for n = 1..92 (terms < 10^12)

Prog

(PARI) isok(k) = eulerphi(k+1) == 5*eulerphi(k); \\ Michel Marcus, Aug 10 2025

Crossrefs

Cf. A000010, A001274, A050472, A067143, A172314.

Sequence in context: A187375 A219749 A219750 * A273879 A321506 A253960

Adjacent sequences: A201250 A201251 A201252 * A201254 A201255 A201256

Keyword

nonn

Author

Ray Chandler, Nov 28 2011

Extensions

a(9)-a(22) from Donovan Johnson, Nov 29 2011

Status

approved