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A014271 Number of trees on n nodes with forbidden limbs. 1
0, 1, 2, 5, 18, 70, 282, 1189, 5144, 22804, 102908, 471477, 2186648, 10247609, 48449798, 230819691, 1106961890, 5339801036, 25891658674, 126123321469, 616916700222, 3028854625890, 14921089624916, 73733085073247, 365384562116904, 1815365194118833 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..25.

T. Lu, The enumeration of trees with and without given limbs, Discr. Math., 154 (1996), 153-165, Example 4.

Index entries for sequences related to trees

FORMULA

G.f. (x-2*x^3+x^5)/[Product_{p>=1} (1-x^p)^(2*a(p))], implicit form. - R. J. Mathar, Feb 27 2016

MATHEMATICA

nmax = 30; b = ConstantArray[0, nmax+1]; b[[1]] = 0; b[[2]] = 1; Do[b[[n+1]] = SeriesCoefficient[(x-2*x^3+x^5) / Product[(1 - x^p)^(2*b[[p+1]]), {p, 1, n-1}], {x, 0, n}], {n, 2, nmax}]; b (* Vaclav Kotesovec, Feb 28 2016 *)

CROSSREFS

Sequence in context: A249062 A322555 A118814 * A073157 A268570 A141494

Adjacent sequences:  A014268 A014269 A014270 * A014272 A014273 A014274

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified October 15 01:40 EDT 2019. Contains 328025 sequences. (Running on oeis4.)