This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A179521 The number of (nontrivial) cycles in the symmetric group S_2n that involve equally many elements in {1,...,n} and {n+1,...,2n}. 1
 0, 1, 10, 183, 7192, 501505, 54163866, 8349297775, 1738661539168, 469966765754097, 159953336512367770, 66922241946410591191, 33756538093718717040600, 20201172267759560773858513, 14150039840975130413592164362, 11468217024458648756976754157295 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..200 FORMULA a(n) = Sum_{k=1..n} (2k-1)! binomial(n,k)^2. MAPLE a:= n-> add((2*k-1)!*binomial(n, k)^2, k=1..n): seq(a(n), n=0..20);  # Alois P. Heinz, Jun 14 2015 PROG (PARI) a(n) = sum(k=1, n, (2*k-1)! * binomial(n, k)^2); \\ Michel Marcus, Aug 14 2013 CROSSREFS Sequence in context: A240405 A304936 A239764 * A211102 A121973 A223146 Adjacent sequences:  A179518 A179519 A179520 * A179522 A179523 A179524 KEYWORD nonn AUTHOR Lukas Brantner (dlbb2(AT)cam.ac.uk), Jul 17 2010 EXTENSIONS More terms from Michel Marcus, Aug 14 2013 STATUS approved

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

Last modified December 5 22:37 EST 2019. Contains 329782 sequences. (Running on oeis4.)