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A009995
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Numbers with digits in strictly decreasing order.
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9
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 21, 30, 31, 32, 40, 41, 42, 43, 50, 51, 52, 53, 54, 60, 61, 62, 63, 64, 65, 70, 71, 72, 73, 74, 75, 76, 80, 81, 82, 83, 84, 85, 86, 87, 90, 91, 92, 93, 94, 95, 96, 97, 98, 210, 310, 320, 321, 410, 420, 421, 430, 431, 432, 510, 520, 521, 530
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| There are precisely 1023 terms (corresponding to every nonempty subset of {0..9}).
A178788(a(n)) = 1. [Reinhard Zumkeller, Jun 30 2010]
A193581(a(n)) > 0 for n > 9. [Reinhard Zumkeller, Aug 10 2011]
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LINKS
| Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
Reinhard Zumkeller, Table of n, a(n) for n = 0..1022, all terms
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MATHEMATICA
| Sort@ Flatten@ Table[FromDigits /@ Subsets[ Range[9, 0, -1], {n}], {n, 10}] (Zak Seidov (zakseidov(AT)yahoo.com), May 10 2006)
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PROG
| (Haskell)
import Data.Set (fromList, minView, insert)
a009995 n = a009995_list !! n
a009995_list = 0 : f (fromList [1..9]) where
f s = case minView s of
Nothing -> []
Just (m, s') -> m : f (foldl (flip insert) s' $
map (10*m +) [0..m `mod` 10 - 1])
-- Reinhard Zumkeller, Aug 10 2011
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CROSSREFS
| Cf. A009993.
Sequence in context: A089583 A032865 A032889 * A190219 A038367 A161350
Adjacent sequences: A009992 A009993 A009994 * A009996 A009997 A009998
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KEYWORD
| nonn,fini,base
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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