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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 Table of n, a(n) for n=1..22. 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 Cf. A000042, A001222, A002275, A004022, A046053. Sequence in context: A299130 A156532 A227435 * A023694 A038465 A103665 Adjacent sequences: A046411 A046412 A046413 * A046415 A046416 A046417 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.)