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A089041
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Inverse binomial transform of squares of factorial numbers.
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5
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1, 0, 3, 26, 453, 11844, 439975, 22056222, 1436236809, 117923229512, 11921584264011, 1455483251191650, 211163237294447053, 35913642489947449356, 7077505637217289437423, 1599980633296779087784934, 411293643476907595937924625, 119299057697083019137937718672
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OFFSET
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0,3
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COMMENTS
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a(n) enumerates (ordered) lists of n two-tuples such that all numbers from 1 to n appear as the first as well as the second tuple entry and the j-th list member is not the tuple (j,j), for every j=1,..,n. Called coincidence-free 2-tuple lists of length n. See the Charalambides reference for this combinatorial interpretation.
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REFERENCES
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Ch. A. Charalambides, Enumerative Combinatorics, Chapman & Hall/CRC, Boca Raton, Florida, 2002, p. 187, Exercise 13.(a), for r=2.
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LINKS
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FORMULA
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G.f.: hypergeom([1, 1, 1], [], x/(1+x))/(1+x).
E.g.f.: exp(-x)* hypergeom([1, 1], [], x).
a(n) = n^2*a(n-1) + n*(n-1)*a(n-2) + (-1)^n. - Vladeta Jovovic, Jul 15 2004
a(n) = Sum_{j=0..n} ((-1)^(n-j))*binomial(n,j)*(j!)^2. See the Charalambides reference a(n)=B_{n,2}.
a(n) = (n-1)*(n+1)*a(n-1) + (n-1)*(2*n-1)*a(n-2) + (n-2)*(n-1)*a(n-3). - Vaclav Kotesovec, Aug 13 2013
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EXAMPLE
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2-tuple combinatorics: a(1)=0 because the only list of 2-tuples with numbers 1 is [(1,1)] and this is a coincidence for j=1.
2-tuple combinatorics: the a(2)=3 coincidence free 2-tuple lists of length n=2 are [(1,2),(2,1)], [(2,1),(1,2)] and [(2,2),(1,1)]. The list [(1,1),(2,2)] has two coincidences (j=1 and j=2).
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MAPLE
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a:= proc(n) option remember;
`if`(n<2, 1-n, n^2*a(n-1)+n*(n-1)*a(n-2)+(-1)^n)
end:
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MATHEMATICA
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Table[n!Sum[(-1)^k(n-k)!/k!, {k, 0, n}], {n, 0, 15}] (* Geoffrey Critzer, Jun 17 2013 *)
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CROSSREFS
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Cf. A001044, A046662 (binomial transform of squares of factorial numbers).
(-1)^n times the polynomials in A099599 evaluated at -1.
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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Charalambides reference and comments with combinatorial examples from Wolfdieter Lang, Jan 21 2008
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STATUS
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approved
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