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A046415
Repunit of length a(n) has exactly 4 prime factors (counted with multiplicity).
2
8, 9, 10, 14, 41, 43, 49, 53, 109, 157, 167, 173, 197, 199, 223, 229, 269, 283, 307, 349
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Repunit
MATHEMATICA
Select[Range[350], PrimeOmega[FromDigits[PadRight[{}, #, 1]]]==4&] (* Harvey P. Dale, Oct 27 2020 *)
PROG
(PARI) isok(n) = bigomega((10^n - 1)/9) == 4; \\ Michel Marcus, Apr 23 2017
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Patrick De Geest, Jul 15 1998
EXTENSIONS
More terms from Robert Gerbicz, Nov 22 2010
Offset corrected to 1, a(18)-a(20) added by Ray Chandler, Apr 23 2017
STATUS
approved