cp's OEIS Frontend

A194720 Number of n-ary words beginning with the first character of the alphabet, that can be built by inserting eight doublets into the initially empty word.

%I A194720 #9 Jul 13 2015 19:08:45
%S A194720 0,1,6435,381333,5068915,33563481,148733571,507709165,1443039123,
%T A194720 3581326065,8006545891,16475259141,31690921395,57644499913,
%U A194720 100028603715,166732334301,268424064211,419229350625,637511191203,946759829365,1376599316211,1963918036281
%N A194720 Number of n-ary words beginning with the first character of the alphabet, that can be built by inserting eight doublets into the initially empty word.
%H A194720 Alois P. Heinz, <a href="/A194720/b194720.txt">Table of n, a(n) for n = 0..1000</a>
%F A194720 G.f.: x * (1 +6427*x +329881*x^2 +2198375*x^3 +3329195*x^4 +1251089*x^5 +91803*x^6 +429*x^7) / (x-1)^8.
%F A194720 a(0) = 0, a(n) = 1 +(14 +(90 +(350 +(910 +(1638 +(2002 +1430 * (n-1)) * (n-1)) * (n-1)) * (n-1)) * (n-1)) * (n-1)) * (n-1) for n>0.
%e A194720 a(1) = 1: a^16 (with 1-ary alphabet {a}).
%p A194720 a:= n-> `if`(n=0, 0, (x-> 1+(14+(90+(350+(910+(1638+(2002+1430*x)*
%p A194720                              x)*x)*x)*x)*x)*x)(n-1)):
%p A194720 seq(a(n), n=0..30);
%Y A194720 Row n=8 of A183134.
%K A194720 nonn
%O A194720 0,3
%A A194720 _Alois P. Heinz_, Sep 02 2011