A210917 - OEIS

%I #15 Aug 02 2021 14:25:36

%S 1,1,4,26,243,2992,45906,845287,18182926,447797646,12327513326,

%T 374460094229,12417692352452,445937963850159,17230880407496706,

%U 712587605616915013,31399448829720502520,1468521294946336416768,72650756455913144620677,3790469182850937732166657

%N Number of transitive reflexive early confluent binary relations R on n labeled elements where |{y : xRy}| <= 9 for all x.

%C R is early confluent iff (xRy and xRz) implies (yRz or zRy) for all x, y, z.

%D A. P. Heinz (1990). Analyse der Grenzen und Möglichkeiten schneller Tableauoptimierung. PhD Thesis, Albert-Ludwigs-Universität Freiburg, Freiburg i. Br., Germany.

%H Alois P. Heinz, <a href="/A210917/b210917.txt">Table of n, a(n) for n = 0..200</a>

%F E.g.f.: t_9(x), where t_k(x) = exp (Sum_{m=1..k} x^m/m! * t_{k-m}(x)) for k>=0 and t_k(x) = 0 otherwise.

%p t:= proc(k) option remember;

%p       `if`(k<0, 0, unapply(exp(add(x^m/m!*t(k-m)(x), m=1..k)), x))

%p     end:

%p gf:= t(9)(x):

%p a:= n-> n!*coeff(series(gf, x, n+1), x, n):

%p seq(a(n), n=0..30);

%t t[k_] := t[k] = If[k<0, 0, Function[x, Exp[Sum[x^m/m!*t[k-m][x], {m, 1, k}]]]]; gf = t[9][x]; a[n_] := n!*SeriesCoefficient[gf, {x, 0, n}]; Table[a[n], {n, 0, 30}] (* _Jean-François Alcover_, Feb 13 2014, translated from Maple *)

%Y Column k=9 of A135302.

%K nonn

%O 0,3

%A _Alois P. Heinz_, Mar 29 2012