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A000776
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n! * (1 + 2*Sum[k=1...n, 1/k]).
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2
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1, 3, 8, 28, 124, 668, 4248, 31176, 259488, 2416032, 24886080, 281004480, 3451887360, 45832538880, 654109585920, 9986000371200, 162391354675200, 2802498609254400, 51156349822771200, 984775394044108800, 19938798081699840000, 423580563732049920000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| a(n-1) equals -1 times the coefficient of x of the characteristic polynomial of the n X n matrix whose (i,j)-entry is equal to i if i=j and is equal to 1 otherwise. - John M. Campbell, May 23, 2011
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REFERENCES
| J. R. Stembridge, Some combinatorial aspects of reduced words in finite Coxeter groups. Trans. Amer. Math. Soc. 349 (1997), no. 4, 1285-1332.
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LINKS
| Nathaniel Johnston, Table of n, a(n) for n = 0..250
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 140
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FORMULA
| E.g.f. (with offset 1): log(1-x)*(log(1-x)-1). [From Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 19 2009]
a(0)=1, a(n+1)=(n+1)*a(n)+2*n!, n>0. [From Sean A. Irvine, Jun 14 2011]
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MAPLE
| a := proc(n) option remember: if(n=0)then return 1: fi: return n*a(n-1)+2*(n-1)!: end: seq(a(n), n=0..21); # Nathaniel Johnston, Jun 14 2011
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MATHEMATICA
| Table[-Coefficient[CharacteristicPolynomial[Array[KroneckerDelta[#1, #2] (((#1)) - 1) + 1 &, {n, n}], x], x], {n, 1, 10}] (* John M. Campbell, May 23, 2011 *)
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CROSSREFS
| Cf. A000774.
Sequence in context: A093356 A135583 A009437 * A000239 A195687 A060707
Adjacent sequences: A000773 A000774 A000775 * A000777 A000778 A000779
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Incorrect formula deleted by Mark van Hoeij (hoeij(AT)math.fsu.edu), Nov 11 2009
Offset corrected by Gary Detlefs, Jul 13 2010
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