A241591 Denominators of Postnikov's hook-length formula 2^n*(n+1)^(n-1)/n!.

1, 1, 1, 3, 3, 5, 45, 315, 35, 567, 14175, 1925, 467775, 868725, 7007, 638512875, 638512875, 14889875, 97692469875, 14849255421, 28868125, 17717861581875, 2143861251406875, 2505147019375, 236682282155319, 284473896821296875, 814172781296875, 3784415134680984375

Offset: 0

Author

N. J. A. Sloane, May 13 2014

Keywords

• nonn
• frac

Examples

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

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

• Matthew Wilson, Bruhat order on fixed-point-free involutions in the symmetric group, Electron. J. Combin., 21(2) (2014), #P2.20.

Crossrefs

Cf. A241590.

Has same start as A248592 but is a different sequence.

Programs

Maple

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

PARI

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