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 A046418 Repunit of length a(n) has exactly 7 prime factors (counted with multiplicity). 2
 12, 20, 21, 22, 27, 35, 61, 65, 74, 82, 85, 141, 146, 177, 187, 194, 226, 299, 323, 329, 337 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..21. P. De Geest, Repunits prime factors Makoto Kamada, Factorizations of 11...11 (Repunit) Eric Weisstein's World of Mathematics, Repunit MATHEMATICA Select[Range[300], PrimeOmega[FromDigits[PadRight[{}, #, 1]]]==7&] (* Harvey P. Dale, Feb 04 2019 *) CROSSREFS Cf. A000042, A001222, A002275, A004022, A004023, A046053. Sequence in context: A175765 A138166 A208273 * A171795 A170806 A038528 Adjacent sequences: A046415 A046416 A046417 * A046419 A046420 A046421 KEYWORD nonn,base,more AUTHOR Patrick De Geest, Jul 15 1998 EXTENSIONS More terms from Robert Gerbicz, Nov 22 2010 Changed offset to 1, a(18) added by Ray Chandler, Apr 23 2017 a(19)-a(21) from Max Alekseyev, May 14 2022 STATUS approved

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