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 A181564 #8 Feb 16 2020 20:50:20 %S A181564 4,6,9,10,15,21,22,25,33,57,58,85,93,133,177,253 %N A181564 Semiprime convenient numbers. %C A181564 This is to semiprimes A001358 as A140768 is to primes A000040. Because Euler's "numerus idoneus" (idoneal, or suitable, or convenient numbers) are finite, this subset is finite. Conjecture: this list is complete (see Weinberger's result and comment by _Jud McCranie_ in A140768). %F A181564 A000926 INTERSECTION A001358. %e A181564 a(16) = A000926(50) = 253 = 11 * 23. %Y A181564 Cf. A001358, A140768. %K A181564 nonn,fini %O A181564 1,1 %A A181564 _Jonathan Vos Post_, Jan 29 2011