A309835 Numbers k such that k + phi(k) is a repunit.

5798663, 5555564201311, 5555574497311, 5555593942711, 66815976110703, 69437045907973255623

Offset

1,1

Comments

Also in the sequence is 555555555555555555555556288388841217550575591423513701223. - Robert Israel, Aug 20 2019

The number 5975946235638859341313216528710061511 is also in the sequence. - Daniel Suteu, Aug 22 2019

Links

Table of n, a(n) for n=1..6.

Example

5798663 is a terms since phi(5798663) = 5312448 and 5798663 + 5312448 = 11111111.

Prog

(PARI) isok(k) = my(d=digits(k+eulerphi(k))); vecmin(d)==1 && vecmax(d)==1; \\ Daniel Suteu, Aug 22 2019

Crossrefs

Subsequence of A116018.

Cf. A000010, A002275, A121048, A244444.

Sequence in context: A017612 A235983 A203931 * A321365 A335255 A250503

Adjacent sequences: A309832 A309833 A309834 * A309836 A309837 A309838

Keyword

nonn,base,more

Author

Giovanni Resta, Aug 19 2019

Extensions

a(5) from Daniel Suteu confirmed by Max Alekseyev, Oct 25 2023

a(6) from Max Alekseyev, Nov 30 2023

Status

approved