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

0,2

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

Links

Table of n, a(n) for n=0..17.

Example

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, ...

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 *)

Crossrefs

Cf. A002110, A109611.

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

Sequence in context: A361807 A233438 A002110 * A376237 A359960 A088257

Adjacent sequences: A118488 A118489 A118490 * A118492 A118493 A118494

Keyword

nonn

Author

Jani Melik, May 05 2006

Status

approved