OFFSET
0,3
COMMENTS
Number of up-down min-max permutations of n elements.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
F. Heneghan and T. K. Petersen, Power series for up-down min-max permutations, 2013.
Masato Kobayashi, A new refinement of Euler numbers on counting alternating permutations, arXiv:1908.00701 [math.CO], 2019.
FORMULA
The e.g.f. can also be written as (1+sin(x))/cos(x)^3.
a(n) ~ n! * n^2*(2/Pi)^(n+3). - Vaclav Kotesovec, May 26 2013
MATHEMATICA
Table[n!*SeriesCoefficient[(1+Sin[x])/Cos[x]^3, {x, 0, n}] , {n, 0, 20}] (* Vaclav Kotesovec, May 26 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 26 2013
STATUS
proposed