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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 May 14 09:34 EDT 2021. Contains 343879 sequences. (Running on oeis4.)