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A108643 Number of binary rooted trees with n nodes and internal path length n. 4
1, 1, 0, 2, 0, 1, 4, 0, 4, 2, 8, 6, 8, 8, 8, 40, 4, 29, 40, 52, 56, 64, 116, 112, 200, 86, 296, 366, 360, 432, 652, 800, 840, 1470, 1116, 2048, 2356, 3052, 3524, 4220, 5648, 6964, 9660, 8688, 14128, 17024, 19432, 23972, 32784, 37873, 44912, 59672, 67560, 93684 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Self-convolution equals A095830 (number of binary trees of path length n). - Paul D. Hanna, Aug 20 2007

REFERENCES

Knuth Vol. 1 Sec. 2.3.4.5, Problem 5.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..500

FORMULA

G.f. = B(w, w) where B(w, z) is defined in A095830.

G.f.: A(x) = 1 + x*(A_2)^2; A_2 = 1 + x^2*(A_3)^2; A_3 = 1 + x^3*(A_4)^2; ... A_n = 1 + x^n*(A_{n+1})^2 for n>=1 with A_1 = A(x). - Paul D. Hanna, Aug 20 2007

MAPLE

A:= proc(n, k) option remember; if n=0 then 1 else convert(series(1+ x^k*A(n-1, k+1)^2, x, n+1), polynom) fi end: a:= n-> coeff(A(n, 1), x, n): seq(a(n), n=0..60);  # Alois P. Heinz, Aug 22 2008

MATHEMATICA

A[n_, k_] := A[n, k] = If[n==0, 1, 1+x^k*A[n-1, k+1]^2 + O[x]^(n+1) // Normal]; a[n_] := SeriesCoefficient[A[n, 1], {x, 0, n}]; Table[a[n], {n, 0, 60}] (* Jean-Fran├žois Alcover, Mar 14 2017, after Alois P. Heinz *)

PROG

(PARI) {a(n)=local(A=1+x*O(x^n)); for(j=0, n-1, A=1+x^(n-j)*A^2); polcoeff(A, n)} - Paul D. Hanna, Aug 20 2007

CROSSREFS

Sequence in context: A039991 A081265 A273821 * A133838 A182138 A258123

Adjacent sequences:  A108640 A108641 A108642 * A108644 A108645 A108646

KEYWORD

nonn

AUTHOR

N. J. A. Sloane and Nadia Heninger, Jul 08 2005

EXTENSIONS

More terms from Vladeta Jovovic, Jul 08 2005

STATUS

approved

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Last modified August 23 01:14 EDT 2017. Contains 290953 sequences.