

A081616


Sequence of constants appearing in formula for expected number of inversions after a sequence of random adjacent transpositions.


1



0, 0, 0, 1, 9, 69, 510, 3740, 27454, 202321, 1498074, 11145324, 83291428, 625022772, 4707757080, 35579447280, 269718129308, 2050317850201, 15625047614946, 119347362039788, 913501931766460, 7005437509949364, 53817428069374328, 414107216180618608
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OFFSET

0,5


REFERENCES

H. Eriksson, K. Ericcson and J. Sjostrand, Expected inversion number after k adjacent transpositions, in Formal Power Series and Algebraic Combinatorics, ed. D. Krob et al., Springer, 2000, pp. 677685.


LINKS

Table of n, a(n) for n=0..23.
N. Eriksen, Expected number of inversions after a sequence of random adjacent transpositions  an exact expression , Discr. Math., 298 (2005), 155168.


FORMULA

See Maple code for formula (found by N. Eriksen).


MAPLE

A081616 := proc(n) local b, s, l; b := binomial; (1/2)*add( b(n1, s1)*(1)^(s1)*4^(ns)*b(2*floor(s/2), floor(s/2))* add( l*b(2*ceil(s/2)1, ceil(s/2)+l ), l=0..floor((s1)/2) ), s=3..n); end;


CROSSREFS

Sequence in context: A125372 A165147 A075045 * A299915 A287818 A297222
Adjacent sequences: A081613 A081614 A081615 * A081617 A081618 A081619


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, Apr 23 2003


STATUS

approved



