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Search: id:A005010
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| 9, 18, 36, 72, 144, 288, 576, 1152, 2304, 4608, 9216, 18432, 36864, 73728, 147456, 294912, 589824, 1179648, 2359296, 4718592, 9437184, 18874368, 37748736, 75497472, 150994944, 301989888, 603979776
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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An autocopy sequence: its first differences are the sequence itself. - Alexandre Wajnberg & Eric Angelini (alexandre.wajnberg(AT)ulb.ac.be), Sep 07 2005
For n>=1, a(n) is equal to the number of functions f:{1,2,...,n+2}->{1,2,3} such that for fixed, different x_1, x_2,...,x_n in {1,2,...,n+2} and fixed y_1, y_2,...,y_n in {1,2,3} we have f(x_i)<>y_i, (i=1,2,...,n). - Milan R. Janjic (agnus(AT)blic.net), May 10 2007
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LINKS
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Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
Tanya Khovanova, Recursive Sequences
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FORMULA
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a(n)= 9*2^n. G.f.: 9/(1-2*x).
a(n) = A118416(n+1,5) for n>4. - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Apr 27 2006
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CROSSREFS
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Row sums of (8, 1)-Pascal triangle A093565.
Adjacent sequences: A005007 A005008 A005009 this_sequence A005011 A005012 A005013
Sequence in context: A109668 A051063 A033896 this_sequence A000547 A138900 A057373
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KEYWORD
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nonn
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AUTHOR
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njas
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