%I #9 Jan 29 2023 13:05:05
%S 1,1,1,3,3,5,17,19,31,45,153,167,287,397,613,1695,2007,3185,4565,6799,
%T 9235,24057,27645,44483,61619,92089,122857,179355,385995,468605,
%U 713849,996331,1441447,1947813,2766657,3659135,7467623,8930629,13471885,18283575,26484639
%N Number of length n word structures with all distinct runlengths using at most 3 symbols.
%H Andrew Howroyd, <a href="/A351639/b351639.txt">Table of n, a(n) for n = 0..1000</a>
%o (PARI) \\ See A351637 for P, R.
%o seq(n)={my(u=P(n)); concat([1], sum(k=1, n, R(u, k)*sum(r=k, 3, binomial(r, k)*(1)^(rk)/r!) ))}
%Y Column k=3 of A351637.
%Y Cf. A351638.
%K nonn
%O 0,4
%A _Andrew Howroyd_, Feb 15 2022
