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A260033
Number of configurations of the general monomer-dimer model for a 2 X 2n square lattice.
2
1, 7, 71, 733, 7573, 78243, 808395, 8352217, 86293865, 891575391, 9211624463, 95173135221, 983314691581, 10159461285307, 104966044432531, 1084493574452273, 11204826469232593, 115766602184825143, 1196083332322900695, 12357755266727364237, 127678491209925526885
OFFSET
0,2
FORMULA
G.f.: (1-4*x+x^2)/(1-11*x+7*x^2-x^3). - Alois P. Heinz, Mar 07 2016
MAPLE
seq(coeff(series((1-4*x+x^2)/(1-11*x+7*x^2-x^3), x, n+1), x, n), n = 0 .. 30); # G. C. Greubel, Oct 27 2019
MATHEMATICA
LinearRecurrence[{11, -7, 1}, {1, 7, 71}, 30] (* G. C. Greubel, Oct 27 2019 *)
PROG
(PARI) my(x='x+O('x^30)); Vec((1-4*x+x^2)/(1-11*x+7*x^2-x^3)) \\ G. C. Greubel, Oct 27 2019
(Magma) R<x>:=PowerSeriesRing(Integers(), 30); Coefficients(R!( (1-4*x+x^2)/(1-11*x+7*x^2-x^3) )); // G. C. Greubel, Oct 27 2019
(Sage)
def A260033_list(prec):
P.<x> = PowerSeriesRing(ZZ, prec)
return P((1-4*x+x^2)/(1-11*x+7*x^2-x^3)).list()
A260033_list(30) # G. C. Greubel, Oct 27 2019
(GAP) a:=[1, 7, 71];; for n in [4..30] do a[n]:=11*a[n-1]-7*a[n-2]+a[n-3]; od; a; # G. C. Greubel, Oct 27 2019
CROSSREFS
Bisection (even part) of A030186.
Sequence in context: A100895 A065537 A048552 * A067307 A334135 A357155
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 19 2015
EXTENSIONS
a(0), a(5)-a(20) from Alois P. Heinz, Mar 07 2016
STATUS
approved