The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 A341965 Adjacent sequences: A180924 A180925 A180926 * A180928 A180929 A180930 KEYWORD nonn,base,easy AUTHOR Jonathan Vos Post, Jan 23 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 3 13:56 EST 2022. Contains 358534 sequences. (Running on oeis4.)