|
| |
|
|
A258495
|
|
Number of words of length 2n such that all letters of the octonary 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
|
|
|
|
1430, 143208, 8488440, 389948856, 15390120042, 549818906780, 18329867191350, 581350326663600, 17769492060922914, 528200606751594392, 15368894406877386408, 439845149792754810984, 12426477142114470011642, 347532158068343623121916, 9642227504194296532321086
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
8,1
|
|
|
LINKS
|
Alois P. Heinz, Table of n, a(n) for n = 8..650
|
|
|
FORMULA
|
a(n) ~ 28^n / (25920*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, 8):
seq(a(n), n=8..25);
|
|
|
CROSSREFS
|
Column k=8 of A256117.
Sequence in context: A244105 A264181 A064305 * A258396 A215548 A274253
Adjacent sequences: A258492 A258493 A258494 * A258496 A258497 A258498
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Alois P. Heinz, May 31 2015
|
|
|
STATUS
|
approved
|
| |
|
|
