OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
S. Heubach and T. Mansour, Enumeration of 3-letter patterns in combinations, arXiv:math/0603285 [math.CO], 2006.
FORMULA
The Heubach/Mansour paper has a complicated g.f.
a(n) ~ c * d^n, where d = 1.948232199887283224240693518762976752988220177086321158242512704029011807341..., c = 0.57609601848694597639954632728322472031509789101742496394456882851645843... - Vaclav Kotesovec, Sep 20 2019
MAPLE
b:= proc(n, t, l) option remember; `if`(n=0, 1, add(
b(n-j, is(j>l), j), j=1..min(n, `if`(t, l, n))))
end:
a:= n-> b(n, false, n):
seq(a(n), n=0..35); # Alois P. Heinz, Oct 24 2017
MATHEMATICA
b[n_, t_, l_] := b[n, t, l] = If[n == 0, 1, Sum[b[n - j, j > l, j], {j, 1, Min[n, If[t, l, n]]}]];
a[n_] := b[n, False, n];
Table[a[n], {n, 0, 35}] (* Jean-François Alcover, Nov 14 2017, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ralf Stephan, May 08 2007
EXTENSIONS
More terms from Vladeta Jovovic, Oct 03 2007
STATUS
approved