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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. 2
2, 5, 10, 24, 52, 121, 258, 616, 1344, 3128, 6996, 16160, 36248, 85041, 191298, 444168, 1019328, 2359392, 5405488, 12625336, 29066304, 67659824, 156911364, 365683744, 849401072, 1987046192, 4624252776, 10816019328 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column sums of A106375.

LINKS

Table of n, a(n) for n=1..28.

FORMULA

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.

EXAMPLE

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).

MAPLE

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)

CROSSREFS

Cf. A106375.

Sequence in context: A316697 A032170 A084081 * A151514 A321007 A253013

Adjacent sequences:  A106373 A106374 A106375 * A106377 A106378 A106379

KEYWORD

nonn

AUTHOR

Emeric Deutsch, May 05 2005

STATUS

approved

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Last modified October 21 20:44 EDT 2019. Contains 328315 sequences. (Running on oeis4.)