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Search: id:A136354
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| A136354 |
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a(n) is the smallest odd composite number m such that m+2 is prime and the set of distinct prime factors of m consists of the first n odd primes. |
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+0
4
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| 9, 15, 105, 3465, 15015, 765765, 33948915, 334639305, 3234846615, 100280245065, 3710369067405, 1369126185872445, 32706903329175075, 307444891294245705, 211829530101735290745, 961380175077106319535, 762374478836145311391255
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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This sequence is different from A070826 and A118750
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EXAMPLE
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a(1)=9 because k=1 with prime factor 3 and 9+2=11, prime
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MATHEMATICA
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Contribution from Farideh Firoozbakht (mymontain(AT)yahoo.com), Aug 12 2009: (Start)
a[n_]:=(c=Product[Prime[k], {k, 2, n+1}]; For[m=1, !(!PrimeQ[c(2m-1)]&&PrimeQ[c
(2m-1)+2]&&Length[FactorInteger[c(2m-1)]]==n), m++ ]; c(2m-1)); Table[a[n], {n, 17}] (End)
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CROSSREFS
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Cf. A136349-A136353 A136355-A136358 A070826 A118750.
Sequence in context: A152219 A029712 A136353 this_sequence A098146 A124274 A075134
Adjacent sequences: A136351 A136352 A136353 this_sequence A136355 A136356 A136357
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KEYWORD
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easy,nonn
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AUTHOR
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Enoch Haga (Enokh(AT)comcast.net), Dec 25 2007
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EXTENSIONS
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Edited, corrected and extended by Farideh Firoozbakht (mymontain(AT)yahoo.com), Aug 12 2009
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