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 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 (list; graph; refs; listen; history; text; internal format)
 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 T. S. Motzkin, Sorting numbers for cylinders and other classification numbers, in Combinatorics, Proc. Symp. Pure Math. 19, AMS, 1971, pp. 167-176. [Annotated, scanned copy] OEIS Wiki, Sorting numbers FORMULA a(n) = 2^n * A000246(n+1). E.g.f.: 1/(sqrt(1+2*x)*(1-2*x)^(3/2)) = 1/(sqrt(1-4*x^2)*(1-2*x)). - Paul Barry, Jul 22 2005 Conjecture: a(n) - 2*a(n-1) - 4*n*(n-1)*a(n-2) = 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: A348767 A335786 A005443 * A235359 A130426 A002397 Adjacent sequences: A002864 A002865 A002866 * A002868 A002869 A002870 KEYWORD nonn,easy AUTHOR EXTENSIONS More terms from James A. Sellers, Jul 10 2000 STATUS approved

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Last modified November 26 20:27 EST 2022. Contains 358362 sequences. (Running on oeis4.)