Search: id:A030981
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%I A030981
%S A030981 1,1,4,11,41,146,564,2199,8835,35989,148912,623008,2633148,11222160,
%T A030981 48181056,208180847,904593623,3950338043,17328256180,76316518987,
%U A030981 337332601513,1495992837550,6654367576732,29681131861564
%N A030981 Noncrossing bushes with n nodes; i.e. rooted noncrossing trees with n 
               nodes and no nonroot nodes of degree 1.
%H A030981 <a href="Sindx_Ro.html#rooted">Index entries for sequences related to 
               rooted trees</a>
%F A030981 Sum((-1)^(n-k)*2^(n-k)*binomial(n, k)*binomial(3*k, k-1), k=1..n)/n; 
               G.f. satisfies z A^3 + 3 z A^2 + z A - A + z = 0
%Y A030981 Sequence in context: A121096 A047091 A121092 this_sequence A151455 A149269 
               A149270
%Y A030981 Adjacent sequences: A030978 A030979 A030980 this_sequence A030982 A030983 
               A030984
%K A030981 nonn
%O A030981 1,3
%A A030981 Emeric Deutsch (deutsch(AT)duke.poly.edu)

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