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 A104874 #13 Nov 01 2019 10:56:31
%S A104874 209,1154,645328246,2445956098,2337448622686,19317973275826,
%T A104874 22894376863198,32220239865718,51087435019342,78382834887262,
%U A104874 163068083613646,176031800345938,622751201209726,1292966939911018
%N A104874 Semiprimes of the form prime(n)*prime(n+1)*prime(n+2)*prime(n+3) - 1.
%C A104874 This is the four-consecutive-prime minus one equivalent of A103533.
%H A104874 Vincenzo Librandi, <a href="/A104874/b104874.txt">Table of n, a(n) for n = 1..1000</a>
%e A104874 n: prime(n) * prime(n+1) * prime(n+2) * prime(n+3) - 1
%e A104874 1: 2 * 3 * 5 * 7 - 1 = 209 = 11 * 19
%e A104874 2: 3 * 5 * 7 * 11 - 1 = 1154 = 2 * 577
%e A104874 36: 151 * 157 * 163 * 167 - 1 = 645328246 = 2 * 322664123
%e A104874 47: 211 * 223 * 227 * 229 - 1 = 2445956098 = 2 * 1222978049
%e A104874 201: 1229 * 1231 * 1237 * 1249 - 1 = 2337448622686 = 2 * 1168724311343.
%t A104874 Bigomega[n_]:=Plus@@Last/@FactorInteger[n]; SemiprimeQ[n_]:=Bigomega[n]==2; Select[Table[Prime[n]*Prime[n+1]*Prime[n+2]*Prime[n+3]-1, {n, 1000}], SemiprimeQ] (* _Ray Chandler_, Mar 29 2005 *)
%Y A104874 Cf. A000040, A001358, A006881, A103533, A103614, A103746, A104875.
%K A104874 easy,nonn
%O A104874 1,1
%A A104874 _Jonathan Vos Post_, Mar 29 2005
%E A104874 Extended by _Ray Chandler_, Mar 29 2005