

A002867


a(n) = binomial(n,floor(n/2))*(n+1)!.
(Formerly M2035 N0806)


3



1, 2, 12, 72, 720, 7200, 100800, 1411200, 25401600, 457228800, 10059033600, 221298739200, 5753767219200, 149597947699200, 4487938430976000, 134638152929280000, 4577697199595520000, 155641704786247680000
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OFFSET

0,2


REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

T. D. Noe, Table of n, a(n) for n = 0..100
Victor Meally, Comparison of several sequences given in Motzkin's paper "Sorting numbers for cylinders...", letter to N. J. A. Sloane, N. D.
T. S. Motzkin, Sorting numbers for cylinders and other classification numbers, in Combinatorics, Proc. Symp. Pure Math. 19, AMS, 1971, pp. 167176. [Annotated, scanned copy]
OEIS Wiki, Sorting numbers


FORMULA

a(n) = 2^n * A000246(n+1).
E.g.f.: 1/(sqrt(1+2*x)*(12*x)^(3/2)) = 1/(sqrt(14*x^2)*(12*x)).  Paul Barry, Jul 22 2005
Conjecture: a(n)  2*a(n1)  4*n*(n1)*a(n2) = 0.  R. J. Mathar, Nov 24 2012


MATHEMATICA

Table[Binomial[n, Floor[n/2]](n+1)!, {n, 0, 20}] (* Harvey P. Dale, Sep 04 2018 *)


CROSSREFS

Cf. A000246.
Sequence in context: A296975 A144086 A005443 * A235359 A130426 A002397
Adjacent sequences: A002864 A002865 A002866 * A002868 A002869 A002870


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms from James A. Sellers, Jul 10 2000


STATUS

approved



