1,1

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]

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

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

Cf. A067933.

Sequence in context: A028906 A118496 A085300 * A093487 A067933 A005234

Adjacent sequences: A119385 A119386 A119387 * A119389 A119390 A119391

nonn

Jorge Coveiro, Jul 25 2006

a(13) from Donovan Johnson, Aug 08 2010

approved