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Search: id:A118491
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| A118491 |
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Product of first n Chen primes. |
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+0
1
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| 1, 2, 6, 30, 210, 2310, 30030, 510510, 9699690, 223092870, 6469693230, 200560490130, 7420738134810, 304250263527210, 14299762385778870, 757887406446280110, 44715356980330526490, 2995928917682145274830
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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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). [From Jonathan Vos Post (jvospost3(AT)gmail.com), Dec 25 2008]
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EXAMPLE
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a(0) = 1 by definition. a(1) = 2, 2 is first Chen prime, a(2) = 6 since it is a product of two first Chen primes 2 and 3, ...
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MAPLE
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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);
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CROSSREFS
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Cf. A002110, A109611.
Cf. A102540. [From Jonathan Vos Post (jvospost3(AT)gmail.com), Dec 25 2008]
Sequence in context: A068215 A096775 A002110 this_sequence A088257 A058694 A046853
Adjacent sequences: A118488 A118489 A118490 this_sequence A118492 A118493 A118494
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KEYWORD
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nonn
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AUTHOR
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Jani Melik (jani_melik(AT)hotmail.com), May 05 2006
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