The On-Line Encyclopedia of Integer Sequences (OEIS)

A225688 revision #9

A225688

E.g.f.: sec(x)^3+(sec(x)^2*tan(x)).

1, 1, 3, 8, 33, 136, 723, 3968, 25953, 176896, 1376643, 11184128, 101031873, 951878656, 9795436563, 104932671488, 1212135593793, 14544442556416, 186388033956483, 2475749026562048, 34859622790687713, 507711943253426176, 7791941518975112403, 123460740095103991808

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OFFSET

0,3

COMMENTS

Number of up-down min-max permutations of n elements.

REFERENCES

F. Heneghan and T. K. Petersen, Power series for up-down min-max permutations,

http://math.depaul.edu/tpeter21/MaxMinUpDownCMJ2v.pdf, 2013.

LINKS

Table of n, a(n) for n=0..23.

FORMULA

The e.g.f. can also be written as (1+sin(x))/cos(x)^3.