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A241590
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Numerators of Postnikov's hook-length formula 2^n*(n+1)^(n-1)/n!.
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2
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1, 2, 6, 64, 250, 1728, 67228, 2097152, 1062882, 80000000, 9431790764, 6115295232, 7168641576148, 64793042714624, 2562890625000, 1152921504606846976, 5724846103019631586, 666334875701477376, 21921547431139208743756, 16777216000000000000000, 164839190645167033716, 513039635408293850333052928
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OFFSET
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0,2
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REFERENCES
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Alexander Postnikov. Permutohedra, associahedra, and beyond. in: Conference in Honor of Richard Stanley's Sixtieth Birthday, June 2004. International Mathematics Research Notices, 6:1026-1106, 2009.
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LINKS
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Table of n, a(n) for n=0..21.
Matthew Wilson, Bruhat order on fixed-point-free involutions in the symmetric group, Electron. J. Combin., 21(2) (2014), #P2.20.
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EXAMPLE
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1, 2, 6, 64/3, 250/3, 1728/5, 67228/45, 2097152/315, 1062882/35, 80000000/567, 9431790764/14175, 6115295232/1925, 7168641576148/467775, ...
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MAPLE
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t1:= [seq(2^n*(n+1)^(n-1)/n!, n=0..50)]:
t2:=map(numer, t1); # A241590
t3:=map(denom, t1); # A241591
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PROG
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(PARI) vector(30, n, n--; numerator(2^n*(n+1)^(n-1)/n!)) \\ Michel Marcus, Jul 18 2015
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CROSSREFS
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Cf. A241591.
Sequence in context: A082640 A139695 A347949 * A052522 A193609 A061999
Adjacent sequences: A241587 A241588 A241589 * A241591 A241592 A241593
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KEYWORD
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nonn,frac
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AUTHOR
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N. J. A. Sloane, May 13 2014
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STATUS
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approved
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