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A074480
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Multiplicative closure of twin prime pair products (A037074).
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5
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1, 15, 35, 143, 225, 323, 525, 899, 1225, 1763, 2145, 3375, 3599, 4845, 5005, 5183, 7875, 10403, 11305, 11663, 13485, 18375, 19043, 20449, 22499, 26445, 31465, 32175, 32399, 36863, 39203, 42875, 46189, 50625, 51983, 53985, 57599, 61705
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A072965(a(n)) = 1.
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
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EXAMPLE
| a(99)=1040399=1019*1021; a(101)=1090125=(3*5)*(3*5)*(3*5)*(17*19); a(103)=1101275=(5*7)*(5*7)*(29*31); a(105)=1126125= (3*5)*(3*5)*(5*7)*(11*13).
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PROG
| (Haskell)
import Data.Set (Set, singleton, delete, findMin, deleteFindMin, insert)
a074480 n = a074480_list !! (n-1)
a074480_list = multClosure a037074_list where
multClosure [] = [1]
multClosure (b:bs) = 1:h [b] (singleton b) bs where
h cs s [] = m:h (m:cs) (foldl (flip insert) s' $ map (*m) cs) []
where (m, s') = deleteFindMin s
h cs s xs'@(x:xs)
| m < x = m:h (m:cs) (foldl (flip insert) s' $ map (*m) cs) xs'
| otherwise = x:h (x:cs) (foldl (flip insert) s $ map (*x) (x:cs)) xs
where (m, s') = deleteFindMin s
-- Reinhard Zumkeller, Aug 14 2011
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CROSSREFS
| Cf. A037074, A001359, A006512, A062505.
Sequence in context: A061367 A070161 A142591 * A194580 A037074 A107423
Adjacent sequences: A074477 A074478 A074479 * A074481 A074482 A074483
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KEYWORD
| nonn,nice
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 23 2002
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