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A078484 Pop-stacks. 2
0, 1, 2, 6, 18, 52, 148, 420, 1192, 3384, 9608, 27280, 77456, 219920, 624416, 1772896, 5033760, 14292288, 40579904, 115217984, 327136896, 928835456, 2637230208, 7487852800, 21260161280, 60363694336, 171389837824, 486624896512, 1381667623424, 3922950583296 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

REFERENCES

M. D. Atkinson and T. Stitt, Restricted permutations and the wreath product, Discrete Math., 259 (2002), 19-36.

FORMULA

G.f.: -x*(1-2*x+2*x^2)/(2*x^3-4*x^2+4*x-1).

CROSSREFS

Sequence in context: A018249 A128104 A027059 * A156989 A077935 A077835

Adjacent sequences:  A078481 A078482 A078483 * A078485 A078486 A078487

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Jan 04 2003

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Last modified February 15 21:27 EST 2012. Contains 205859 sequences.