login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A082970 Number of permutations of length n containing 2 occurrences of 132. 4
4, 23, 107, 464, 1950, 8063, 33033, 134576, 546312, 2212550, 8946454, 36134656, 145831270, 588199815, 2371435125, 9557736480, 38511326040, 155143873170, 624899673690, 2516678580000, 10134353299980, 40805797511622 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

LINKS

Table of n, a(n) for n=4..25.

T. Mansour and A. Vainshtein, Counting occurrences of 132 in a permutation, arXiv:math/0105073 [math.CO], 2001.

FORMULA

a(n) = C(2*n-6,n-2)*(n^3+17*n^2-80*n+80)/(2n(n-1)).

MATHEMATICA

Table[Binomial[2n-6, n-2] (n^3+17n^2-80n+80)/(2n(n-1)), {n, 4, 30}] (* Harvey P. Dale, Dec 25 2018 *)

PROG

(PARI) a(n)=binomial(2*n-6, n-2)*(n^3+17*n^2-80*n+80)/2/n/(n-1)

CROSSREFS

Column k=2 of A263771.

Sequence in context: A038381 A241777 A321614 * A197868 A017973 A306669

Adjacent sequences:  A082967 A082968 A082969 * A082971 A082972 A082973

KEYWORD

nonn

AUTHOR

Benoit Cloitre, May 27 2003

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 18 02:19 EDT 2020. Contains 337164 sequences. (Running on oeis4.)