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A143402
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Expansion of x^k/Prod_{t=k..2k}(1-tx) for k=7.
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2
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0, 0, 0, 0, 0, 0, 0, 1, 84, 3990, 141120, 4138827, 106469748, 2484848080, 53791898160, 1096912870053, 21307466872692, 397605494092170, 7173885616672320, 125794299357058879, 2152559266567924116, 36065247772657686660, 593280221500152370800
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OFFSET
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0,9
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COMMENTS
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a(n) is also the number of forests of 7 labeled rooted trees of height at most 1, with n labels, where any root may contain >= 1 labels.
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LINKS
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Alois P. Heinz, Table of n, a(n) for n = 0..300
Index entries for sequences related to rooted trees
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FORMULA
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G.f.: x^7/((1-7x)(1-8x)(1-9x)(1-10x)(1-11x)(1-12x)(1-13x)(1-14x)).
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MAPLE
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a := proc(k::nonnegint) local M; M := Matrix(k+1, (i, j)-> if (i=j-1) then 1 elif j=1 then [seq(-1* coeff (product (1-t*x, t=k..2*k), x, u), u=1..k+1)][i] else 0 fi); p-> (M^p)[1, k+1] end(7): seq (a(n), n=0..30);
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CROSSREFS
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7th column of A143395.
Sequence in context: A035806 A017747 A223959 * A004379 A075906 A075909
Adjacent sequences: A143399 A143400 A143401 * A143403 A143404 A143405
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KEYWORD
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nonn
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AUTHOR
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Alois P. Heinz, Aug 12 2008
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STATUS
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approved
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