A052890 - OEIS

%I #13 Oct 30 2025 15:09:42

%S 1,1,2,6,16,49,153,493,1623,5460,18625,64373,224843,792546,2815443,

%T 10070115,36233440,131063713,476320360,1738401482,6368750019,

%U 23413000913,86342448134,319329672079,1184129737292,4401635480735,16398478453303,61220441044887

%N A simple grammar.

%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=866">Encyclopedia of Combinatorial Structures 866</a>

%p spec := [S,{B=Set(C,1 <= card),C=Prod(Z,S),S=PowerSet(B)},unlabeled]: seq(combstruct[count](spec,size=n), n=0..20);

%K easy,nonn

%O 0,3

%A _INRIA Encyclopedia of Combinatorial Structures_, Jan 25 2000

%E More terms from _Sean A. Irvine_, Dec 01 2021