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A029136
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Expansion of 1/((1-x^2)*(1-x^3)*(1-x^4)*(1-x^6)).
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0
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1, 0, 1, 1, 2, 1, 4, 2, 5, 4, 7, 5, 11, 7, 13, 11, 17, 13, 23, 17, 27, 23, 33, 27, 42, 33, 48, 42, 57, 48, 69, 57, 78, 69, 90, 78, 106, 90, 118, 106, 134, 118, 154, 134, 170, 154, 190, 170, 215, 190, 235, 215, 260, 235
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,5
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COMMENTS
| Number of nonisomorphic hollow hexagons with n hexagons for n >= 8 (a class of primitive coronoids).
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REFERENCES
| B. N. Cyvin et al., Enumeration of conjugated hydrocarbons..., Structural Chem., 6 (1995), 85-88, equations (1)-(5) and (24).
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MAPLE
| M := Matrix(15, (i, j)-> if (i=j-1) or (j=1 and member(i, [2, 3, 4, 11, 12, 13])) then 1 elif j=1 and member(i, [5, 7, 8, 10, 15]) then -1 else 0 fi); a := n -> (M^(n))[1, 1]; seq (a(n), n=0..53); - Alois P. Heinz (heinz(AT)hs-heilbronn.de), Jul 25 2008
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CROSSREFS
| Sequence in context: A106044 A124896 A008742 * A001479 A128861 A161307
Adjacent sequences: A029133 A029134 A029135 * A029137 A029138 A029139
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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