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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, 1207959552, 2415919104
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| The 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
9 times powers of 2. [From Omar E. Pol (info(AT)polprimos.com), Dec 16 2008]
a(n) = A173786(n+3,n) for n>2. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 28 2010]
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..235
Index entries for sequences related to linear recurrences with constant coefficients
Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
Tanya Khovanova, Recursive Sequences
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FORMULA
| 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)gmail.com), Apr 27 2006
a(n)=2*a(n-1), n>0 ; a(0)=9 . [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Nov 23 2008]
a(n) = A000079(n)*9 = A020714(n)*3. [From Omar E. Pol (info(AT)polprimos.com), Dec 16 2008]
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MATHEMATICA
| 9*2^Range[0, 60] (* From Vladimir Joseph Stephan Orlovsky, June 09 2011 *)
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PROG
| (MAGMA) [9*2^n: n in [0..40]]; // Vincenzo Librandi, Apr 28 2011
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CROSSREFS
| Row sums of (8, 1)-Pascal triangle A093565.
Cf. A000079, A020714. [From Omar E. Pol (info(AT)polprimos.com), Dec 16 2008]
Sequence in context: A162689 A033896 A195332 * A000547 A138900 A202187
Adjacent sequences: A005007 A005008 A005009 * A005011 A005012 A005013
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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