cp's OEIS Frontend

A321035 Number of words of length 3n such that all letters of the quinary alphabet occur at least once and are introduced in ascending order and which can be built by repeatedly inserting triples of identical letters into the initially empty word.

%I A321035 #4 Oct 26 2018 16:12:12
%S A321035 273,15300,564585,17493938,495445275,13337746758,348484836788,
%T A321035 8943435290790,227093583305420,5731575551864799,144208756776131553,
%U A321035 3624029726937528334,91079326041351533935,2291027079046386970458,57709725323735510918970,1456179679670608615334480
%N A321035 Number of words of length 3n such that all letters of the quinary alphabet occur at least once and are introduced in ascending order and which can be built by repeatedly inserting triples of identical letters into the initially empty word.
%H A321035 Alois P. Heinz, <a href="/A321035/b321035.txt">Table of n, a(n) for n = 5..773</a>
%p A321035 b:= (n, k)-> `if`(n=0, 1, k/n*add(binomial(3*n, j)*(n-j)*(k-1)^j, j=0..n-1)):
%p A321035 a:= n-> (k-> add((-1)^i*b(n, k-i)/(i!*(k-i)!), i=0..k))(5):
%p A321035 seq(a(n), n=5..25);
%Y A321035 Column k=5 of A256311.
%K A321035 nonn
%O A321035 5,1
%A A321035 _Alois P. Heinz_, Oct 26 2018