This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A052796 E.g.f.: x^4*exp(x)^2. 2
 0, 0, 0, 0, 24, 240, 1440, 6720, 26880, 96768, 322560, 1013760, 3041280, 8785920, 24600576, 67092480, 178913280, 467927040, 1203240960, 3048210432, 7620526080, 18827182080, 46022000640, 111421685760, 267412045824, 636695347200, 1504916275200 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS a(n) is the number of ways that n people can form two distinct committees and then choose a president and vice president for each committee. LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 753 FORMULA Recurrence: {a(1)=0, a(2)=0, a(3)=0, a(4)=24, (-2*n-2)*a(n)+(n-3)*a(n+1)} O.g.f.:-24*x^4/(2*x-1)^5 [From Maksym Voznyy (voznyy(AT)mail.ru), Aug 12 2009] a(n) = (n-3)*(n-2)*(n-1)*n * 2^(n-4). - Vaclav Kotesovec, Nov 27 2012 MAPLE spec := [S, {B=Set(Z), S=Prod(Z, Z, Z, Z, B, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); MATHEMATICA Range[0, 30]!* CoefficientList[Series[Exp[x]^2 * x^4, {x, 0, 30}], x] (* Vincenzo Librandi, Dec 06 2012 *) PROG (MAGMA) [(n-3)*(n-2)*(n-1)*n * 2^(n-4): n in [0..30]]; // Vincenzo Librandi, Dec 06 2012 CROSSREFS Equals A090802(n, 4). Sequence in context: A192491 A167548 A192849 * A056269 A000919 A014340 Adjacent sequences:  A052793 A052794 A052795 * A052797 A052798 A052799 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 2000 EXTENSIONS More terms from Vincenzo Librandi, Dec 06 2012 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .