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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A226882 Number of n-length words w over ternary alphabet {a,b,c} such that #(w,a) >= #(w,b) >= #(w,c) >= 1, where #(w,x) counts the letters x in word w. 3
6, 12, 50, 180, 497, 1484, 5154, 13680, 41327, 134508, 368095, 1095367, 3521156, 9733564, 29025290, 92208816, 257946527, 769203752, 2428043309, 6848294497, 20442949562, 64191187508, 182286409175, 544512163065, 1702858693902, 4861764643419, 14531465607434 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 3..1000

Vaclav Kotesovec, Recurrence (of order 9)

FORMULA

a(n) ~ 3^n/6 * (1 + 3*sqrt(3/(Pi*n))/2+sqrt(3)*(1+2*cos(2*Pi*n/3))/(Pi*n)). - Vaclav Kotesovec, Aug 29 2014

EXAMPLE

a(4) = 12: aabc, aacb, abac, abca, acab, acba, baac, baca, bcaa, caab, caba, cbaa.

MATHEMATICA

Table[Sum[n!/Product[IntegerPartitions[n, {3}][[k, j]]!, {j, 1, 3}], {k, 1, Length[IntegerPartitions[n, {3}]]}], {n, 3, 30}] (* Vaclav Kotesovec, Aug 29 2014 *)

CROSSREFS

Column k=3 of A226874.

Sequence in context: A106692 A032470 A018809 * A214903 A256584 A117866

Adjacent sequences:  A226879 A226880 A226881 * A226883 A226884 A226885

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jun 21 2013

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 November 17 13:33 EST 2019. Contains 329230 sequences. (Running on oeis4.)