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A225689 E.g.f.: sec(x)^2*tan(x)+sec(x)*tan(x)^2. 4
0, 1, 2, 8, 28, 136, 662, 3968, 24568, 176896, 1326122, 11184128, 98329108, 951878656, 9596075582, 104932671488, 1192744081648, 14544442556416, 183983154281042, 2475749026562048, 34489251602450188, 507711943253426176, 7722592644581974502, 123460740095103991808, 2035778987564783402728 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Number of up-down max-min 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 sin(x)*(1+sin(x))/cos(x)^3.

A225688(n)+a(n) = A000111(n+2). - corrected by Vaclav Kotesovec, May 26 2013

a(n) ~ n! * n^2*(2/Pi)^(n+3). - Vaclav Kotesovec, May 26 2013

MATHEMATICA

Table[n!*SeriesCoefficient[Sin[x]*(1+Sin[x])/Cos[x]^3, {x, 0, n}] , {n, 0, 20}] (* Vaclav Kotesovec, May 26 2013 *)

CROSSREFS

Cf. A000111, A225688.

Sequence in context: A307940 A150731 A150732 * A216785 A261559 A061230

Adjacent sequences:  A225686 A225687 A225688 * A225690 A225691 A225692

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, May 26 2013

STATUS

approved

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Last modified September 18 20:34 EDT 2019. Contains 327181 sequences. (Running on oeis4.)