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A225495
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Numbers having only weak prime factors, cf. A051635.
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5
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1, 3, 7, 9, 13, 19, 21, 23, 27, 31, 39, 43, 47, 49, 57, 61, 63, 69, 73, 81, 83, 89, 91, 93, 103, 109, 113, 117, 129, 131, 133, 139, 141, 147, 151, 161, 167, 169, 171, 181, 183, 189, 193, 199, 207, 217, 219, 229, 233, 241, 243, 247, 249, 267, 271, 273, 279
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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PROG
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(Haskell)
import Data.Set (singleton, fromList, union, deleteFindMin)
a225495 n = a225495_list !! (n-1)
a225495_list = 1 : h (singleton p) ps [p] where
(p:ps) = a051635_list
h s xs'@(x:xs) ys
| m > x = h (s `union` (fromList $ map (* x) (1 : ys))) xs ys
| otherwise = m : h (s' `union` (fromList $ map (* m) ys')) xs' ys'
where ys' = m : ys; (m, s') = deleteFindMin s
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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