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Search: id:A020989
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| 1, 6, 26, 106, 426, 1706, 6826, 27306, 109226, 436906, 1747626, 6990506, 27962026, 111848106, 447392426, 1789569706, 7158278826, 28633115306, 114532461226, 458129844906, 1832519379626, 7330077518506
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OFFSET
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0,2
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COMMENT
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Let Zb[n](x) = polynomial in x whose coefficients are the corresponding digits of index n in base b. Then Z2[(5*4^k-2)/3](1/tau) = 1 - Marc LeBrun (mlb(AT)well.com), Mar 01 2001
a(n)=number of derangements of [2n+2] with runs consisting of consecutive integers. E.g. a(1)=6 because the derangements of {1,2,3,4} with runs consisting of consecutive integers are 4|123, 34|12, 4|3|12, 4|3|2|1, 234|1, and 34|2|1 (the bars delimit the runs). - Emeric Deutsch (deutsch(AT)duke.poly.edu), May 26 2003
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REFERENCES
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J. Brillhart and P. Morton, A case study in mathematical research: the Golay-Rudin-Shapiro sequence, Amer. Math. Monthly, 103 (1996) 854-869.
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FORMULA
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a(0)=1, a(n) = 4*a(n-1) + 2; a(n) = a(n-1)+ 5*{4^(n-1)}; - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), May 27 2001
a(n+1)=2(a(n))+2(a(n)+1), a(1)=1 - Simone Severini (ss54(AT)york.ac.uk), Sep 25 2005
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CROSSREFS
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A column of A119726.
Sequence in context: A034560 A037545 A027996 this_sequence A079675 A113991 A124465
Adjacent sequences: A020986 A020987 A020988 this_sequence A020990 A020991 A020992
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KEYWORD
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nonn
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AUTHOR
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njas
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