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

Author

Jorge Coveiro, Jul 25 2006

Keywords

• nonn

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]

Crossrefs

Cf. A067933.

Programs

PARI

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

Extensions

a(13) from Donovan Johnson, Aug 08 2010