Search: id:A106376
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%I A106376
%S A106376 2,5,10,24,52,121,258,616,1344,3128,6996,16160,36248,85041,191298,
%T A106376 444168,1019328,2359392,5405488,12625336,29066304,67659824,156911364,
%U A106376 365683744,849401072,1987046192,4624252776,10816019328
%N A106376 Number of binary trees (each vertex has 0, or 1 left, or 1 right, or 
               2 children) with n edges and having all leaves at the same level.
%C A106376 Column sums of A106375.
%F A106376 See the Maple program where a recurrence relation for the triangle A106375(n, 
               k) is given; A106376(k) is the sum of the terms in column k of this 
               triangle.
%e A106376 a(3)=10 because we have eight paths of length 3 (each edge can have two 
               orientations) and two trees in the shape of the letter Y (the bottom 
               edge can have two orientations).
%p A106376 a:=proc(n,k) if n=1 and k=1 then 2 elif n=1 and k=2 then 1 elif n=1 then 
               0 elif k=1 then 0 else 2*a(n-1,k-1) + add(a(n-1,j)*a(n-1,k-2-j),j=1..k-3) 
               fi end: seq(add(a(n,k),n=1..k),k=1..15); # a(n,k)=A106375(n,k)
%Y A106376 Cf. A106375.
%Y A106376 Sequence in context: A026754 A032170 A084081 this_sequence A151514 A001431 
               A054866
%Y A106376 Adjacent sequences: A106373 A106374 A106375 this_sequence A106377 A106378 
               A106379
%K A106376 nonn
%O A106376 1,1
%A A106376 Emeric Deutsch (deutsch(AT)duke.poly.edu), May 05 2005

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