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A046414 Repunit of length a(n) has exactly 3 prime factors (counted with multiplicity). 1
13, 31, 37, 38, 67, 73, 83, 97, 101, 103, 113, 127, 149, 163, 191, 227, 241, 263, 313, 331, 373, 379 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
467 <= a(23) <= 857. 857, 1303, 1483, 2267 are terms of this sequence. - Chai Wah Wu, Nov 03 2019
LINKS
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
Sequence in context: A299130 A156532 A227435 * A023694 A038465 A103665
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

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Last modified February 26 12:54 EST 2024. Contains 370352 sequences. (Running on oeis4.)