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A046415
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Repunit of length a(n) has exactly 4 prime factors (counted with multiplicity).
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1
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8, 9, 10, 14, 41, 43, 49, 53, 109, 157, 167, 173, 197, 199, 223, 229, 269, 283, 307, 349
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OFFSET
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1,1
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LINKS
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Eric Weisstein's World of Mathematics, Repunit
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MATHEMATICA
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Select[Range[350], PrimeOmega[FromDigits[PadRight[{}, #, 1]]]==4&] (* Harvey P. Dale, Oct 27 2020 *)
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PROG
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(PARI) isok(n) = bigomega((10^n - 1)/9) == 4; \\ Michel Marcus, Apr 23 2017
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CROSSREFS
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KEYWORD
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nonn,base,more
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AUTHOR
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EXTENSIONS
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Offset corrected to 1, a(18)-a(20) added by Ray Chandler, Apr 23 2017
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STATUS
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approved
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