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A128358 Numbers k such that k divides 18^k - 1. 16
1, 17, 289, 4913, 83521, 1419857, 5846759, 24054337, 24137569, 99394903, 408923729, 410338673, 1689713351, 6951703393, 6975757441, 28725126967, 118178957681, 118285781329, 118587876497, 486643291847, 488327158439 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

17 divides a(n) for n > 1.

a(n) = 17^(n-1) for n < 7.

a(7) = 20231*17^2.

LINKS

Table of n, a(n) for n=1..21.

PROG

(PARI) is(n)=Mod(18, n)^n==1 \\ Charles R Greathouse IV, Nov 04 2016

CROSSREFS

Cf. A001026 (powers of 17), A015969 (k divides 16^k + 1).

Sequence in context: A045607 A045606 A171291 * A015969 A001026 A178765

Adjacent sequences:  A128355 A128356 A128357 * A128359 A128360 A128361

KEYWORD

hard,nonn

AUTHOR

Alexander Adamchuk, Mar 01 2007

EXTENSIONS

a(8)-a(10) from Farideh Firoozbakht, Mar 05 2007

a(11)-a(19) from Ryan Propper, Dec 31 2007

a(20)-a(24) from Alexander Adamchuk, May 17 2010

STATUS

approved

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Last modified November 27 16:35 EST 2021. Contains 349394 sequences. (Running on oeis4.)