The On-Line Encyclopedia of Integer Sequences (OEIS)

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A111308

Sum_{k=1..n} k!! * (n+1-k)!!, where k!! = k*(k-2)*(k-4)..*(1 or 2).
(history; published version)

#7 by Charles R Greathouse IV at Wed Apr 09 10:16:39 EDT 2014

AUTHOR

Leroy Quet , Nov 03 2005

Discussion

Wed Apr 09

10:16

OEIS Server: https://oeis.org/edit/global/2155

#6 by N. J. A. Sloane at Wed Feb 05 20:18:14 EST 2014

AUTHOR

_Leroy Quet _ Nov 03 2005

Discussion

Wed Feb 05

20:18

OEIS Server: https://oeis.org/edit/global/2118

#5 by N. J. A. Sloane at Thu Oct 31 12:17:31 EDT 2013

MATHEMATICA

Table[ Sum[k!!(n + 1 - k)!!, {k, n}], {n, 25}] (* _Robert G. Wilson v _ *)

Discussion

Thu Oct 31

12:17

OEIS Server: https://oeis.org/edit/global/2036

#4 by Charles R Greathouse IV at Sat Jul 14 11:40:54 EDT 2012

EXTENSIONS

More terms from _Robert G. Wilson v (rgwv(at)rgwv.com), _, Nov 04 2005

Discussion

Sat Jul 14

11:40

OEIS Server: https://oeis.org/edit/global/1816

#3 by N. J. A. Sloane at Sat Oct 02 03:00:00 EDT 2010

LINKS

Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> (listed in lieu of email address)

KEYWORD

easy,nonn,new

#2 by N. J. A. Sloane at Fri Jan 09 03:00:00 EST 2009

LINKS

Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> (listed in lieu of email address)

KEYWORD

easy,nonn,new

AUTHOR

Leroy Quet (qq-quet(AT)mindspring.com), Nov 03 2005

#1 by N. J. A. Sloane at Tue Jan 24 03:00:00 EST 2006

NAME

Sum_{k=1..n} k!! * (n+1-k)!!, where k!! = k*(k-2)*(k-4)..*(1 or 2).

DATA

0, 1, 4, 10, 28, 71, 204, 556, 1716, 5049, 16884, 53418, 193500, 654639, 2560140, 9209016, 38697300, 147193425, 661035060, 2645445870, 12627252540, 52926443415, 267088884300, 1167777120420, 6200158778100, 28178714373705

OFFSET

0,3

EXAMPLE

a(5) = 1 *5*3*1 + 2 *4*2 + 3*1 *3*1 + 4*2 *2 + 5*3*1 *1 = 15 + 16 + 9 + 16 + 15 = 71.

MATHEMATICA

Table[ Sum[k!!(n + 1 - k)!!, {k, n}], {n, 25}] (* Robert G. Wilson v *)

CROSSREFS

Cf. A006882.

KEYWORD

easy,nonn

AUTHOR

Leroy Quet (qq-quet(AT)mindspring.com), Nov 03 2005

EXTENSIONS

More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Nov 04 2005

STATUS

approved