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A119388 Numbers n such that n == -1 (mod phi(n-1)). 0
2, 3, 5, 7, 11, 31, 71, 511, 2591, 131071, 3359231, 167247871, 8589934591 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence has the terms from A067933 (all primes), plus 511 and 3359231 that are not primes.

Checked up to x<70000000

a(14) > 10^11. [From Donovan Johnson, Aug 08 2010]

LINKS

Table of n, a(n) for n=1..13.

PROG

(PARI) for(x=1, 70000000, if(((x)+1)%eulerphi((x)-1)==0, print((x))))

CROSSREFS

Cf. A067933.

Sequence in context: A028906 A118496 A085300 * A093487 A067933 A005234

Adjacent sequences:  A119385 A119386 A119387 * A119389 A119390 A119391

KEYWORD

nonn

AUTHOR

Jorge Coveiro, Jul 25 2006

EXTENSIONS

a(13) from Donovan Johnson, Aug 08 2010

STATUS

approved

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Last modified July 26 12:20 EDT 2021. Contains 346294 sequences. (Running on oeis4.)