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A181476 Numbers n such that n^n=1 [mod sigma(n)]. 0
1, 2, 8, 9, 36, 128, 576, 625, 900, 1156, 2304, 2601, 5185, 6561, 10082, 10404, 27225, 32768, 57600, 117649, 181476, 260100, 285156, 367236, 378225, 443521, 607825, 617796, 645248, 656100, 665856, 783225, 1115136, 1394450, 1500625, 1782225 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

If p is prime then p^k is in the sequence iff k is of the form p^t-1

where t is a nonnegative integer.

LINKS

Table of n, a(n) for n=1..36.

MATHEMATICA

Join[{1},

Select[Range[1800000], PowerMod[ #, #, DivisorSigma[1, # ]]==1 &]]

CROSSREFS

Cf. A000203, A177006.

Sequence in context: A088825 A181887 A221049 * A055678 A301281 A091793

Adjacent sequences:  A181473 A181474 A181475 * A181477 A181478 A181479

KEYWORD

nonn

AUTHOR

Farideh Firoozbakht, May 23 2010

STATUS

approved

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Last modified August 10 12:19 EDT 2020. Contains 336379 sequences. (Running on oeis4.)