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A020869
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Number of single component forests in Moebius ladder M_n.
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0
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34, 222, 1280, 6955, 36378, 185178, 923696, 4535991, 22000490, 105640634, 503067648, 2379006071, 11183747330, 52306745310, 243553038816, 1129612848795, 5221079904978, 24057393297286, 110543216068160
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,1
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REFERENCES
| J. P. McSorley, Counting structures in the Moebius ladder, Discrete Math., 184 (1998), 137-164.
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FORMULA
| G.f.=x^2*(3x^8-27x^7+126x^6-360x^5+663x^4-781x^3+570x^2-220x+34)/[(1-x)^3*(1-5x+3x^2-x^3)^2]. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 21 2004
The McSorley reference gives the approximation a(n)~.8757*n*4.3652^n-1.5432*n*.4786^n*cos(.8458*n+.9674)+n^2-2*n. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 21 2004
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MAPLE
| G:=x^2*(3*x^8-27*x^7+126*x^6-360*x^5+663*x^4-781*x^3+570*x^2-220*x+34)/(1-x)^3/(1-5*x+3*x^2-x^3)^2: Gser:=series(G, x=0, 27): seq(coeff(Gser, x^n), n=2..25); (Deutsch)
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CROSSREFS
| Sequence in context: A074900 A058581 A050263 * A055716 A020872 A183319
Adjacent sequences: A020866 A020867 A020868 * A020870 A020871 A020872
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 21 2004
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