login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A258492 Number of words of length 2n such that all letters of the quinary alphabet occur at least once and are introduced in ascending order and which can be built by repeatedly inserting doublets into the initially empty word. 2
42, 1485, 34034, 647920, 11187462, 182587701, 2880017910, 44477796451, 677940669900, 10250875770135, 154278143783022, 2316262521915440, 34742240691197182, 521131993897607925, 7822497290908844702, 117554364707534272375, 1769075045150700563052 (list; graph; refs; listen; history; text; internal format)
OFFSET

5,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 5..800

FORMULA

a(n) ~ 16^n / (54*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 01 2015

MAPLE

A:= proc(n, k) option remember; `if`(n=0, 1, k/n*

      add(binomial(2*n, j)*(n-j)*(k-1)^j, j=0..n-1))

    end:

T:= (n, k)-> add((-1)^i*A(n, k-i)/(i!*(k-i)!), i=0..k):

a:= n-> T(n, 5):

seq(a(n), n=5..25);

CROSSREFS

Column k=5 of A256117.

Sequence in context: A121974 A096048 A215301 * A067638 A155021 A270410

Adjacent sequences:  A258489 A258490 A258491 * A258493 A258494 A258495

KEYWORD

nonn

AUTHOR

Alois P. Heinz, May 31 2015

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 June 26 04:11 EDT 2019. Contains 324369 sequences. (Running on oeis4.)