VOOZH about

URL: https://oeis.org/A258497

⇱ A258497 - OEIS

login
A258497
Number of words of length 2n such that all letters of the denary 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
16796, 2735810, 255290156, 17977098425, 1063758951255, 55927419074670, 2700837720153300, 122411464503168984, 5284666028132079380, 219622926821644989478, 8855064908059488718600, 348436223706779520860457, 13441577595226619289460295, 510180504585665885463323546
OFFSET
10,1
COMMENTS
In general, column k>2 of A256117 is asymptotic to (4*(k-1))^n / ((k-2)^2 * (k-2)! * sqrt(Pi) * n^(3/2)). - Vaclav Kotesovec, Jun 01 2015
LINKS
FORMULA
a(n) ~ 36^n / (2580480*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, 10):
seq(a(n), n=10..25);
CROSSREFS
Column k=10 of A256117.
Sequence in context: A243836 A244107 A264183 * A258398 A215550 A227600
KEYWORD
nonn
AUTHOR
Alois P. Heinz, May 31 2015
STATUS
approved