This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A180922 #15 Apr 10 2021 10:32:45 %S A180922 8,12,102,1001,10002,100006,1000002,10000005,100000006,1000000003, %T A180922 10000000001,100000000006,1000000000001,10000000000001, %U A180922 100000000000018,1000000000000002,10000000000000006,100000000000000007,1000000000000000001,10000000000000000007 %N A180922 Smallest n-digit number that is divisible by exactly 3 primes (counted with multiplicity). %C A180922 This is to 3 as smallest n-digit semiprime A098449 is to 2, and as smallest n-digit prime A003617 is to 1. Smallest n-digit triprime. Smallest n-digit 3-almost prime. %e A180922 a(1) = 8 because 8=2^3 is the smallest (only) 1-digit number divisible by exactly 3 primes (counted with multiplicity). %e A180922 a(2) = 12 because 12 = 2^2 * 3 is the smallest of the (21) 2-digit numbers divisible by exactly 3 primes (counted with multiplicity). %e A180922 a(3) = 102 because 102 = 2 * 3 * 17 is the smallest 3-digit numbers divisible by exactly 3 primes (counted with multiplicity). %o A180922 (PARI) A180922(n)=for(n=10^(n-1),10^n-1,bigomega(n)==3&return(n)) \\ _M. F. Hasler_, Jan 23 2011 %o A180922 (Python) %o A180922 from sympy import factorint %o A180922 def triprimes(n): f = factorint(n); return sum(f[p] for p in f) == 3 %o A180922 def a(n): %o A180922 an = max(1, 10**(n-1)) %o A180922 while not triprimes(an): an += 1 %o A180922 return an %o A180922 print([a(n) for n in range(1, 21)]) # _Michael S. Branicky_, Apr 10 2021 %Y A180922 Cf. A003617, A014612, A098449. %K A180922 nonn,base,easy %O A180922 1,1 %A A180922 _Jonathan Vos Post_, Jan 23 2011