OFFSET
1,1
COMMENTS
a(7) > 10^13. - Giovanni Resta, Jul 13 2015
MATHEMATICA
Do[ If[ Mod[ DivisorSigma[1, n], n - 1] == 0, Print[n] ], {n, 2, 10^8} ]
PROG
(PARI) is(n)=sigma(n)%(n-1)==0 \\ Anders Hellström, Aug 15 2015
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert G. Wilson v, Dec 04 2000
EXTENSIONS
a(6) from Donovan Johnson, Nov 15 2009
STATUS
approved