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A136807 Hankel transform of double factorial numbers n!*2^n=A000165(n). 2
1, 4, 256, 589824, 86973087744, 1282470362637926400, 2723154477021188283432960000, 1133321924829207204666583887642624000000, 120746421332702772771144114237731253721340313600000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

By the properties of the Hankel transform, a(n)=2^(n(n+1))*A055209(n).

Also Hankel transform of A000354, A010844, A082032. - Philippe Deléham, Jan 23 2008

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..28

Michael Z. Spivey and Laura L. Steil, The k-Binomial Transforms and the Hankel Transform, Journal of Integer Sequences, Vol. 9 (2006), Article 06.1.1.

FORMULA

a(n) = Product_{k=1..n} (2k)^(2(n-k+1)).

a(n) ~ 2^((n+1)^2) * Pi^(n+1) * n^(n^2 + 2*n + 5/6) / (A^2 * exp(3*n^2/2 + 2*n - 1/6)), where A is the Glaisher-Kinkelin constant A074962. - Vaclav Kotesovec, Feb 24 2019

MATHEMATICA

Table[Product[(2k)^(2(n-k+1)), {k, n}], {n, 0, 10}] (* Harvey P. Dale, Apr 11 2013 *)

PROG

(PARI) for(n=0, 10, print1(prod(k=1, n, (2*k)^(2*(n-k+1))), ", ")) \\ G. C. Greubel, Oct 14 2018

(MAGMA) [1] cat [(&*[(2*k)^(2*(n-k+1)): k in [1..n]]): n in [1..10]]; // G. C. Greubel, Oct 14 2018

CROSSREFS

Cf. A000354, A010844, A082032, A055209.

Sequence in context: A207284 A229100 A060757 * A057156 A132656 A137840

Adjacent sequences:  A136804 A136805 A136806 * A136808 A136809 A136810

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Jan 23 2008

STATUS

approved

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Last modified June 19 07:33 EDT 2019. Contains 324218 sequences. (Running on oeis4.)