login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A110371 a(n)=[(n+1)(n+2)(n+3)...(2n)]/(1+2+3+...+n). 1
2, 4, 20, 168, 2016, 31680, 617760, 14414400, 392071680, 12189864960, 426645273600, 16606346803200, 711700577280000, 33307587016704000, 1690360041097728000, 92472637542405120000, 5425061402487767040000, 339780161524233830400000, 22629358757513973104640000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n)=2(n-1)!*Catalan(n). a(n)=2*A065866(n-1). - Emeric Deutsch, Aug 05 2005

LINKS

Table of n, a(n) for n=1..19.

Ron Knott, 2016, January 2016.

FORMULA

{2*(2n)!}/{(n+1)!*n}

EXAMPLE

a(4) = 5*6*7*8/10 = 168.

a(5) = 10*9*8*7*6/(5+4+3+2+1) = 2016.

MAPLE

seq(2*(2*n)!/(n+1)!/n, n=1..20); # Emeric Deutsch, Aug 05 2005

MATHEMATICA

Table[(Times@@Range[n+1, 2n])/((n(n+1))/2), {n, 20}] (* or *) Table[ 2(n-1)! CatalanNumber[n], {n, 20}] (* Harvey P. Dale, Jul 15 2016 *)

PROG

(PARI) A110371(n)=binomial(2*n, n-1)/n*(n-1)!*2 \\ M. F. Hasler, Jan 31 2016

CROSSREFS

Cf. A065866.

Sequence in context: A102087 A357671 A052573 * A120388 A061348 A127103

Adjacent sequences: A110368 A110369 A110370 * A110372 A110373 A110374

KEYWORD

easy,nonn

AUTHOR

Amarnath Murthy, Jul 24 2005

EXTENSIONS

More terms from Emeric Deutsch, Aug 05 2005

Edited by M. F. Hasler, Jan 31 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 26 21:15 EST 2022. Contains 358362 sequences. (Running on oeis4.)