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Search: id:A143938
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| A143938 |
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The Wiener index of a benzenoid consisting of a linear chain of n hexagons. |
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+0
2
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| 27, 109, 279, 569, 1011, 1637, 2479, 3569, 4939, 6621, 8647, 11049, 13859, 17109, 20831, 25057, 29819, 35149, 41079, 47641, 54867, 62789, 71439, 80849, 91051, 102077, 113959, 126729, 140419, 155061, 170687, 187329, 205019, 223789, 243671
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OFFSET
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1,1
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FORMULA
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a(n)=(1/3)(16n^3 + 36n^2 + 26n + 3).
G.f.=z(27+z+5z^2-z^3)/(1-z)^4.
a(n)=Sum(k*A143937(n,k),k=1..2n+1).
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EXAMPLE
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a(1)=27 because in a hexagon we have 6 distances equal to 1, 6 distances equal to 2 and 3 distances equal to 3 (6*1+6*2+3*3=27).
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MAPLE
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seq((16*n^3+36*n^2+26*n+3)*1/3, n = 1 .. 35)
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CROSSREFS
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A143937
Sequence in context: A129026 A042426 A042424 this_sequence A042428 A158554 A029699
Adjacent sequences: A143935 A143936 A143937 this_sequence A143939 A143940 A143941
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KEYWORD
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nonn
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Sep 06 2008
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