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 A180927 Largest n-digit number that is divisible by exactly 3 primes (counted with multiplicity). 1
 8, 99, 994, 9994, 99997, 999994, 9999994, 99999994, 999999998, 9999999995, 99999999998, 999999999998, 9999999999998, 99999999999998, 999999999999995, 9999999999999998, 99999999999999998, 999999999999999987, 9999999999999999999 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This is to 3 and A014612, as 2 and A098450 (largest n-digit semiprime), and as 1 and A003618 (Largest n-digit prime). Largest n-digit triprime. Largest n-digit 3-almost prime. LINKS EXAMPLE a(1) = 8 because 8 = 2^3 is the largest (only) 1-digit number that is divisible by exactly 3 primes (counted with multiplicity). a(2) = 99 because 99 = 3^2 * 11 is the largest 2-digit number (of 21) that is divisible by exactly 3 primes (counted with multiplicity). a(3) = 994 because 994 = 2 * 7 * 71 is the largest 3-digit number that is divisible by exactly 3 primes (counted with multiplicity). MATHEMATICA lndn3[n_]:=Module[{k=10^n-1}, While[PrimeOmega[k]!=3, k--]; k]; Array[ lndn3, 20] (* Harvey P. Dale, Jul 25 2019 *) PROG (PARI) A180927(n)=forstep(n=10^n-1, 10^(n-1), -1, bigomega(n)==3&return(n))  \\ - M. F. Hasler, Jan 23 2011 CROSSREFS Cf. A003618, A014612, A098450, A180922. Sequence in context: A299513 A299313 A300114 * A091801 A050919 A230343 Adjacent sequences:  A180924 A180925 A180926 * A180928 A180929 A180930 KEYWORD nonn,base,easy AUTHOR Jonathan Vos Post, Jan 23 2011 STATUS approved

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Last modified September 21 04:59 EDT 2019. Contains 327253 sequences. (Running on oeis4.)