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Search: id:A010790
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| 1, 2, 12, 144, 2880, 86400, 3628800, 203212800, 14631321600, 1316818944000, 144850083840000, 19120211066880000, 2982752926433280000, 542861032610856960000, 114000816848279961600000
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OFFSET
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0,2
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COMMENT
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Let M_n be the symmetrical n X n matrix M_n(i,j)=1/min(i,j); then for n>=0 det(M_n)=(-1)^(n-1)/a(n-1) - Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 27 2002
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REFERENCES
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J. H. Conway and R. K. Guy, The Book of Numbers, Copernicus Press, NY, 1996, pp. 63-65.
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..100
Index entries for sequences related to factorial numbers
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FORMULA
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Integral representation as n-th moment of a positive function on a positive half axis, in Maple notation: a(n)=int(x^n*2*sqrt(x)*BesselK(1, 2*sqrt(x)), x=0..infinity), n=0, 1... Hypergeometric g.f.: a(0)=1, a(n)=subs(x=0, n!*diff(1/((x-1)^2), x$n)), n=1, 2... - Karol A. Penson (penson(AT)lptl.jussieu.fr), Oct 23 2001
Sum i=0..inf 1/a(i) = BesselI(1, 2) - 1 (where 1 is order, 2 is value) - Gerald McGarvey (Gerald.McGarvey(AT)comcast.net), Jun 10 2004
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MAPLE
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f := n->n!*(n+1)!;
seq(add((count(Permutation(k)))^2, k=0..n), n=0..14); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Oct 17 2006
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CROSSREFS
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Cf. A004737, A000290.
Second column of triangle A129065.
Sequence in context: A052740 A052742 A035049 this_sequence A086928 A001927 A105558
Adjacent sequences: A010787 A010788 A010789 this_sequence A010791 A010792 A010793
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KEYWORD
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nonn,nice,easy
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AUTHOR
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njas
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