A241590 Numerators of Postnikov's hook-length formula 2^n*(n+1)^(n-1)/n!.

1, 2, 6, 64, 250, 1728, 67228, 2097152, 1062882, 80000000, 9431790764, 6115295232, 7168641576148, 64793042714624, 2562890625000, 1152921504606846976, 5724846103019631586, 666334875701477376, 21921547431139208743756, 16777216000000000000000, 164839190645167033716, 513039635408293850333052928

Offset

0,2

References

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.

Links

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.

Example

1, 2, 6, 64/3, 250/3, 1728/5, 67228/45, 2097152/315, 1062882/35, 80000000/567, 9431790764/14175, 6115295232/1925, 7168641576148/467775, ...

Maple

t1:= [seq(2^n*(n+1)^(n-1)/n!, n=0..50)]:
t2:=map(numer, t1); # A241590
t3:=map(denom, t1); # A241591

Mathematica

Join[{1}, Table[(2^n (n+1)^(n-1))/n!, {n, 30}]//Numerator] (* Harvey P. Dale, Feb 23 2023 *)

Prog

(PARI) vector(30, n, n--; numerator(2^n*(n+1)^(n-1)/n!)) \\ Michel Marcus, Jul 18 2015

Crossrefs

Cf. A241591.

Sequence in context: A082640 A139695 A347949 * A052522 A193609 A061999

Adjacent sequences: A241587 A241588 A241589 * A241591 A241592 A241593

Keyword

nonn,frac

Author

N. J. A. Sloane, May 13 2014

Status

approved