OFFSET
1,2
COMMENTS
Or, numbers n such that phi(n) divides n*(n-1). - Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 14 2006
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
9 is in the sequence because phi(9) = 6. 9 % 6 = 3 and 9^2 % 6 = 3. But 10 is not in the sequence because phi(10) = 4 and 10 % 4 = 6 and 10^2 % 4 = 0.
PROG
(PARI) isok(n) = ((n^2 - n) % eulerphi(n)) == 0 \\ Michel Marcus, Jun 07 2013
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Igor Naverniouk (igor(AT)lexansoft.com), Jul 14 2002
STATUS
approved