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A087433
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Expansion of (1-2*x)*(1-4*x+x^2)/((1-x)*(1-3*x)*(1-4*x)).
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2
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1, 2, 6, 20, 70, 252, 926, 3460, 13110, 50252, 194446, 758100, 2973350, 11716252, 46333566, 183739940, 730176790, 2906358252, 11582386286, 46200404980, 184414199430, 736494536252, 2942491360606, 11759505089220, 47006639297270
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Binomial transform of A087432. a(n+1)=2*A085282(n).
Counts closed walks of length 2n at a vertex of the cyclic graph on 12 nodes C_12. - Herbert Kociemba (kociemba(AT)t-online.de), Jun 06 2004
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..1000
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FORMULA
| a(n)=0^n/6+1/3+3^n/3+4^n/6
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PROG
| (MAGMA) [0^n/6+1/3+3^n/3+4^n/6: n in [0..30]]; // Vincenzo Librandi, Aug 12 2011
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CROSSREFS
| Sequence in context: A065346 A071976 A000984 * A119373 A151284 A049138
Adjacent sequences: A087430 A087431 A087432 * A087434 A087435 A087436
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Sep 02 2003
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EXTENSIONS
| Definition corrected by Herbert Kociemba (kociemba(AT)t-online.de), Jun 06 2004.
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