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A329550 Total number of consecutive triples of the form (odd, even, odd) or (even, odd, even) in all permutations of [n]. 2
0, 0, 0, 2, 16, 108, 864, 7200, 69120, 705600, 8064000, 97977600, 1306368000, 18441561600, 281652940800, 4533271142400, 78111748915200, 1412288317440000, 27115935694848000, 544201764986880000, 11524272670310400000, 254238259854458880000, 5887622859787468800000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

All terms are even.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..449

FORMULA

a(n) = Sum_{k>=1} k * A152877(n,k).

a(n) ~ n! * n / 4. - Vaclav Kotesovec, Nov 19 2019

EXAMPLE

a(3) = 2: 123, 321.

MAPLE

a:= proc(n) option remember; `if`(n<5, [0$3, 2, 16][n+1],

     (n-2)*(2*(n-4)*a(n-1)+(n-3)^2*n*a(n-2))/(n-3)/(n-4))

    end:

seq(a(n), n=0..30);

CROSSREFS

Cf. A152877.

Sequence in context: A009619 A012024 A193217 * A208137 A207435 A301940

Adjacent sequences:  A329547 A329548 A329549 * A329551 A329552 A329553

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Nov 16 2019

STATUS

approved

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Last modified June 13 18:45 EDT 2021. Contains 345008 sequences. (Running on oeis4.)