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!)
A321033 Number of words of length 3n such that all letters of the ternary alphabet occur at least once and are introduced in ascending order and which can be built by repeatedly inserting triples into the initially empty word. 2
12, 198, 2520, 29886, 347907, 4048966, 47431488, 560528820, 6684500548, 80402461416, 974694481735, 11899112853684, 146175947513247, 1805742311925206, 22417900292210960, 279556262002954608, 3500139320096264886, 43982137867266022438, 554494988892196104240 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 3..889

MAPLE

b:= (n, k)-> `if`(n=0, 1, k/n*add(binomial(3*n, j)*(n-j)*(k-1)^j, j=0..n-1)):

a:= n-> (k-> add((-1)^i*b(n, k-i)/(i!*(k-i)!), i=0..k))(3):

seq(a(n), n=3..25);

CROSSREFS

Column k=3 of A256311.

Sequence in context: A034671 A066230 A262845 * A048667 A115865 A291285

Adjacent sequences:  A321030 A321031 A321032 * A321034 A321035 A321036

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Oct 26 2018

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 October 18 13:21 EDT 2021. Contains 348067 sequences. (Running on oeis4.)