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 A087433 Expansion of (1-2*x)*(1-4*x+x^2)/((1-x)*(1-3*x)*(1-4*x)). 2
 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; text; internal format)
 OFFSET 0,2 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, Jun 06 2004 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (8,-19,12). FORMULA a(n)=0^n/6+1/3+3^n/3+4^n/6 MATHEMATICA CoefficientList[Series[(1-2x)(1-4x+x^2)/((1-x)(1-3x)(1-4x)), {x, 0, 30}], x] (* Harvey P. Dale, Nov 26 2014 *) PROG (MAGMA) [0^n/6+1/3+3^n/3+4^n/6: n in [0..30]]; // Vincenzo Librandi, Aug 12 2011 CROSSREFS Sequence in context: A065346 A071976 A000984 * A119373 A151284 A049138 Adjacent sequences:  A087430 A087431 A087432 * A087434 A087435 A087436 KEYWORD easy,nonn AUTHOR Paul Barry, Sep 02 2003 EXTENSIONS Definition corrected by Herbert Kociemba, Jun 06 2004. STATUS approved

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