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A027434
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a(1) = 2; then defined by property that a(n) = smallest number > a(n-1) such that successive runs have lengths 1,1,2,2,3,3,4,4.
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3
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2, 3, 4, 4, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n) = A027709(n)/2. - Tanya Khovanova (tanyakh(AT)yahoo.com), Mar 04 2008
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REFERENCES
| Sam Speed, An integer sequence (preprint).
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LINKS
| William A. Tedeschi, Table of n, a(n) for n = 1..10000
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FORMULA
| a(n) = 1+[ sqrt(4n-3) ].
a(n) = ceil(2*sqrt(n)). [Mircea Merca, Feb 07 2012]
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PROG
| (Haskell)
a027434 n = a027434_list !! (n-1)
a027434_list = 2 : concat (map (\x -> replicate (x `div` 2) x) [3..])
-- Reinhard Zumkeller, Nov 22 2011
(PARI) a(n)=sqrtint(4*n-3)+1 \\ Charles R Greathouse IV, Feb 07 2012
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CROSSREFS
| A027434(n)=A049068(n)-n.
Sequence in context: A172005 A200247 A056791 * A174697 A176504 A196162
Adjacent sequences: A027431 A027432 A027433 * A027435 A027436 A027437
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KEYWORD
| nonn,nice,easy,changed
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AUTHOR
| Sam Speed (SPEEDS(AT)msci.memphis.edu)
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EXTENSIONS
| More terms from Courtney Clipp (cclipp(AT)ashland.edu), Dec 08 2004
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