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 A118491 #8 Jun 06 2022 10:29:37
%S A118491 1,2,6,30,210,2310,30030,510510,9699690,223092870,6469693230,
%T A118491 200560490130,7420738134810,304250263527210,14299762385778870,
%U A118491 757887406446280110,44715356980330526490,2995928917682145274830
%N A118491 Product of first n Chen primes.
%C A118491 This first differs from primorials A002110 at a(14) = 14299762385778870 = 47*a(13) rather than 43*a(13) because 43 is the smallest prime that is not a Chen prime (A102540). - _Jonathan Vos Post_, Dec 25 2008
%e A118491 a(0) = 1 by definition. a(1) = 2, 2 is first Chen prime, a(2) = 6 since it is the product of the first two Chen primes 2 and 3, ...
%p A118491 ischenprime:=proc(n); if (isprime(n) = 'true') then if (isprime(n+2) = 'true' or numtheory[bigomega](n+2) = 2) then RETURN('true') else RETURN('false') fi fi end: ts_chen_prim_numbers:=proc(n) local i,ans,tren; ans:=[1]: tren:=1: for i from 1 to n do if (ischenprime(i) = 'true') then tren := i*tren: ans:=[op(ans), tren]: fi od; RETURN(ans) end: ts_chen_prim_numbers(140);
%t A118491 FoldList[Times,Join[{1},Select[Prime[Range[50]],PrimeOmega[#+2]<3&]]] (* _Harvey P. Dale_, Jun 06 2022 *)
%Y A118491 Cf. A002110, A109611.
%Y A118491 Cf. A102540. - _Jonathan Vos Post_, Dec 25 2008
%K A118491 nonn
%O A118491 0,2
%A A118491 _Jani Melik_, May 05 2006