A218094 Number of transitive reflexive early confluent binary relations R on n labeled elements with max_{x}(|{y : xRy}|) = 4.

75, 1035, 16025, 267715, 4798983, 92374107, 1913052805, 42483670075, 1008618127825, 25519311555595, 686016182577453, 19536602119711495, 587778832750221385, 18633924653894097385, 620967800006345098353, 21703395396687678061639, 793901738815689934686095

Offset

4,1

Comments

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

References

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

Links

Alois P. Heinz, Table of n, a(n) for n = 4..200

Formula

E.g.f.: t_4(x)-t_3(x), with t_k(x) = exp (Sum_{m=1..k} x^m/m! * t_{k-m}(x)) if k>=0 and t_k(x) = 0 else.

a(n) = A210912(n) - A210911(n).

Maple

t:= proc(k) option remember; `if`(k<0, 0,
      unapply(exp(add(x^m/m! *t(k-m)(x), m=1..k)), x))
    end:
egf:= t(4)(x)-t(3)(x):
a:= n-> n!* coeff(series(egf, x, n+1), x, n):
seq(a(n), n=4..20);

Mathematica

m = 4; t[k_] := t[k] = If[k<0, 0, Function[x, Exp[Sum[x^m/m!*t[k-m][x], {m, 1, k}]]]] ; egf = t[m][x]-t[m-1][x]; a[n_] := n!*Coefficient[Series[egf, {x, 0, n+1}], x, n]; Table[a[n], {n, m, 20}] (* Jean-François Alcover, Feb 14 2014, after Maple *)

Crossrefs

Column k=4 of A135313.

Sequence in context: A251249 A264673 A320618 * A285920 A293581 A210047

Adjacent sequences: A218091 A218092 A218093 * A218095 A218096 A218097

Keyword

nonn

Author

Alois P. Heinz, Oct 20 2012

Status

approved