OFFSET
1,1
COMMENTS
467 <= a(23) <= 857. 857, 1303, 1483, 2267 are terms of this sequence. - Chai Wah Wu, Nov 03 2019
LINKS
P. De Geest, Repunits prime factors
Makoto Kamada, Factorizations of 11...11 (Repunit)
Eric Weisstein's World of Mathematics, Repunit
EXAMPLE
a(n)=13 so 1111111111111 = 53*79*265371653.
PROG
(PARI) is(n)=bigomega(10^n\9)==3 \\ Charles R Greathouse IV, Mar 11 2014
CROSSREFS
KEYWORD
nonn,more,base
AUTHOR
Patrick De Geest, Jul 15 1998
EXTENSIONS
More terms from Robert Gerbicz, Nov 22 2010
More terms from Bo Gyu Jeong, Jun 12 2012
STATUS
approved