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A103998
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Number of dimer tilings of a 4 x 2n Moebius strip.
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1
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1, 11, 71, 539, 4271, 34276, 276119, 2226851, 17965151, 144948419, 1169523076, 9436433171, 76139155439, 614339685971, 4956888901511, 39995380044004, 322708555336511, 2603821045832171, 21009309912323639
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| G.f.: (1-25x^2+22x^3-3x^4)/(1-11x+25x^2-11x^3+x^4).
a(0)=1, a(1)=11, a(2)=71, a(3)=539, a(4)=4271, a(n)=11*a(n-1)-25*a(n-2)+ 11*a(n-3)-a(n-4) [From Harvey P. Dale, June 15 2011]
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MATHEMATICA
| Join[{1}, LinearRecurrence[{11, -25, 11, -1}, {11, 71, 539, 4271}, 40]] (* or *) CoefficientList[ Series[ (1-25x^2+22x^3-3x^4)/ (1-11x+ 25x^2- 11x^3+x^4), {x, 0, 40}], x] (* From Harvey P. Dale, June 15 2011 *)
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CROSSREFS
| Cf. Second row of array A103997.
Sequence in context: A199488 A068847 A139185 * A160587 A034196 A092044
Adjacent sequences: A103995 A103996 A103997 * A103999 A104000 A104001
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KEYWORD
| nonn
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AUTHOR
| Ralf Stephan, Feb 26 2005
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