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 A102415 #18 Feb 16 2025 08:32:55
%S A102415 4,6,10,10,15,15,22,26,26,35,39,39,46,51,58,58,65,69,69,77,82,87,95,
%T A102415 95,95,106,106,111,123,129,134,134,146,146,155,161,166,169,178,178,
%U A102415 187,187,194,194,209,221,226,226,226,237,237,249,254,262,267,267,274,278,278
%N A102415 Greatest semiprime less than n-th prime.
%H A102415 Amiram Eldar, <a href="/A102415/b102415.txt">Table of n, a(n) for n = 3..10000</a>
%H A102415 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Semiprime.html">Semiprime</a>
%F A102415 a(n) < A000040(n) < A102414(n).
%e A102415 a(3) = 4 since 4 is the greatest semiprime less than prime(3) = 5.
%t A102415 a[n_] := Module[{m = Prime[n] - 1}, While[PrimeOmega[m] != 2, m--]; m]; Array[a, 60, 3] (* _Amiram Eldar_, Feb 06 2020 *)
%o A102415 (PARI) a(n) = {sp = prime(n)-1; while(bigomega(sp) != 2, sp--); sp;} \\ _Michel Marcus_, Mar 04 2017
%Y A102415 Cf. A001358, A102414, A102440.
%K A102415 nonn
%O A102415 3,1
%A A102415 _Reinhard Zumkeller_, Jan 08 2005