A118491 Product of first n Chen primes.

1, 2, 6, 30, 210, 2310, 30030, 510510, 9699690, 223092870, 6469693230, 200560490130, 7420738134810, 304250263527210, 14299762385778870, 757887406446280110, 44715356980330526490, 2995928917682145274830

Offset: 0

Author

Jani Melik, May 05 2006

Keywords

• nonn

Comments

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

Examples

			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, ...
		

Crossrefs

Cf. A002110, A109611.

Cf. A102540. - Jonathan Vos Post, Dec 25 2008

Programs

Maple

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);

Mathematica

FoldList[Times,Join[{1},Select[Prime[Range[50]],PrimeOmega[#+2]<3&]]] (* Harvey P. Dale, Jun 06 2022 *)