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%I #15 Jan 27 2021 05:30:50
%S 8,99,994,9994,99997,999994,9999994,99999994,999999998,9999999995,
%T 99999999998,999999999998,9999999999998,99999999999998,
%U 999999999999995,9999999999999998,99999999999999998,999999999999999987,9999999999999999999
%N Largest n-digit number that is divisible by exactly 3 primes (counted with multiplicity).
%C 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.
%e a(1) = 8 because 8 = 2^3 is the largest (only) 1-digit number that is divisible by exactly 3 primes (counted with multiplicity).
%e 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).
%e a(3) = 994 because 994 = 2 * 7 * 71 is the largest 3-digit number that is divisible by exactly 3 primes (counted with multiplicity).
%t lndn3[n_]:=Module[{k=10^n-1},While[PrimeOmega[k]!=3,k--];k]; Array[ lndn3,20] (* _Harvey P. Dale_, Jul 25 2019 *)
%o (PARI) A180927(n)=forstep(n=10^n-1,10^(n-1),-1,bigomega(n)==3&return(n)) \\ _M. F. Hasler_, Jan 23 2011
%Y Cf. A003618, A014612, A098450, A180922.
%K nonn,base,easy
%O 1,1
%A _Jonathan Vos Post_, Jan 23 2011
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