A218105 - OEIS

%I #17 Aug 02 2021 08:20:43

%S 0,1,11592,1812216,92374107,3151808478,94494907584,2755081426548,

%T 81009491387682,2437976801668408,75638497021149062,

%U 2427804103875438288,80751743315656443940,2784897386029995089700,99580133563729334883624,3690405873805797826482120

%N Number of transitive reflexive early confluent binary relations R on n+5 labeled elements with max_{x}(|{y : xRy}|) = n.

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

%H Alois P. Heinz, <a href="/A218105/b218105.txt">Table of n, a(n) for n = 0..200</a>

%F a(n) = A135313(n+5,n).

%p t:= proc(k) option remember; `if` (k<0, 0, unapply(exp(add(x^m/m! *t(k-m)(x), m=1..k)), x)) end: tt:= proc(k) option remember; unapply((t(k)-t(k-1))(x), x) end: T:= proc(n, k) option remember; coeff(series(tt(k)(x), x, n+1), x, n) *n! end:

%p a:= n-> T(n+5,n): seq(a(n), n=0..20);

%t m = 5; f[0, _] = 1; f[k_, x_] := f[k, x] = Exp[Sum[x^m/m!*f[k-m, x], {m, 1, k}]]; (* t = A135302 *) t[0, 0] = 1; t[_, 0] = 0; t[n_, k_] := t[n, k] = SeriesCoefficient[f[k, x], {x, 0, n}]*n!; a[0] = 0; a[n_] := t[n+m, n]-t[n+m, n-1]; Table[a[n], {n, 0, 20}] (* _Jean-François Alcover_, Feb 14 2014 *)

%Y Cf. A135313.

%K nonn

%O 0,3

%A _Alois P. Heinz_, Oct 20 2012