The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.


(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A271213 a(n) = 2^(n-2) * (n! + floor(n/2)!) 1

%I #6 Nov 07 2016 09:02:34

%S 1,1,3,14,104,976,11616,161472,2582016,46451712,929003520,20437463040,

%T 490498375680,12752940072960,357082301399040,10712468463943680,

%U 342798990185594880,11655165645170933760,419585963202371911680,15944266600833991311360,637770664032408384307200

%N a(n) = 2^(n-2) * (n! + floor(n/2)!)

%C a(n) is the number of rearrangement patterns, i.e., the number of rearrangement map equivalence classes.

%D J. Burns, Counting a Class of Signed Permutations and Chord Diagrams related to DNA Rearrangement, Preprint.

%H J. Burns, <a href="">Table of Rearrangement Maps and Patterns for n = 1, 2, and 3</a>.

%F a(n)=2^(n-2)*(n!+floor(n/2)!)

%F a(n)~(pi*n/8)^(1/2) (2n/e)^n

%e For n=1 the a(1)=1 solution is the equivalence class {+1,-1}.For n=2 the a(2)=3 solutions are the equivalence classes {+1+2, -2-1}, {+1-2, +2-1, -2+1, -1+2}, and {+2+1, -1-2}

%t Table[2^(n-2)*(n!+Floor[n/2]!),{n,10}]

%Y Partition of A000165 into equivalence classes.

%Y Cf. A271214, A271216, A271217.

%K nonn,easy

%O 0,3

%A _Jonathan Burns_, Apr 02 2016

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 May 19 00:35 EDT 2024. Contains 372666 sequences. (Running on oeis4.)