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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 (list; graph; refs; listen; history; text; internal format)
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

Alois P. Heinz, Table of n, a(n) for n = 10..650

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

Adjacent sequences:  A258494 A258495 A258496 * A258498 A258499 A258500

KEYWORD

nonn

AUTHOR

Alois P. Heinz, May 31 2015

STATUS

approved

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Last modified March 3 14:58 EST 2021. Contains 341762 sequences. (Running on oeis4.)