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 A242134 #22 Feb 10 2022 22:53:49 %S A242134 3,31,265,2326,20753,186657,1694289,15522934,143361278,1332987907, %T A242134 12466213899,117166026836,1105962031475,10478814259427,99613914990801, %U A242134 949727475528388,9078425620890083,86983554771459735,835176988544997091,8034305823411044844,77423350444120266442 %N A242134 Number of semiprimes with n digits. %F A242134 a(n) = A066265(n) - A066265(n-1). - _Jens Kruse Andersen_, Aug 16 2014 %e A242134 4, 6, and 9 are semiprimes with 1 digit. So a(1) = 3. %o A242134 (PARI) vector(8,n,sum(k=10^(n-1),10^n-1,bigomega(k)==2)) %Y A242134 Cf. A001358, A066265. %K A242134 nonn,hard,base %O A242134 1,1 %A A242134 _Derek Orr_, Aug 15 2014 %E A242134 a(9)-a(18) from A066265, added by _Jens Kruse Andersen_, Aug 16 2014 %E A242134 a(19)-a(21) from A066265, added by _Jon E. Schoenfield_, Feb 10 2022