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A036251 Number of trees with 2-colored leaves. 2
1, 2, 3, 3, 7, 14, 35, 85, 231, 633, 1845, 5461, 16707, 51945, 164695, 529077, 1722279, 5664794, 18813369, 62996850, 212533226, 721792761, 2466135375, 8471967938, 29249059293, 101440962296, 353289339927, 1235154230060 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..27.

Index entries for sequences related to trees

FORMULA

G.f.: B(x) + B(x)^2/2 + B(x^2)/2 - B(x)*(B(x)-x), where B(x) is g.f. for A029856.

MATHEMATICA

max = 30; B[_] = 1; Do[B[x_] = x*Exp[Sum[(B[x^k] + x^k)/k + O[x]^n, {k, 1, n}]] // Normal, {n, 1, max}]; A[x_] = 1 + x + x^2 + B[x] - B[x]^2/2 + B[x^2]/2; CoefficientList[A[x] + O[x]^max, x] (* Jean-François Alcover, Jan 28 2019 *)

CROSSREFS

Essentially the same as A036250. Cf. A038054.

Sequence in context: A129012 A136122 A121875 * A176022 A316275 A113031

Adjacent sequences:  A036248 A036249 A036250 * A036252 A036253 A036254

KEYWORD

nonn

AUTHOR

Christian G. Bower, Nov 15 1998

STATUS

approved

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Last modified July 16 23:49 EDT 2019. Contains 325092 sequences. (Running on oeis4.)