A119388 Numbers n such that n == -1 (mod phi(n-1)).

2, 3, 5, 7, 11, 31, 71, 511, 2591, 131071, 3359231, 167247871, 8589934591

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