login
This site is supported by donations to The OEIS Foundation.

 

Logo

The submissions stack has been unacceptably high for several months now. Please voluntarily restrict your submissions and please help with the editing. (We don't want to have to impose further limits.)

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A135413 Number of at most 4-way branching ordered (i.e. plane) trees. 1
1, 2, 6, 20, 70, 246, 875, 3144, 11385, 41470, 151778, 557712, 2056210, 7602700, 28180050, 104677280, 389571983, 1452293766, 5422187130, 20271296100, 75878518695, 284339792110, 1066585128810, 4004566131000, 15048213795600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Obtained by Lagrange inversion of the generating function for at most k-way branching trees.

Solve z = T/(1+T+...T^k) when k = 4. I.e. the n-th term is the coefficient of x^{n-1} in the expansion of (1+x+x^2+x^3+x^4)^n.

LINKS

Table of n, a(n) for n=1..25.

FORMULA

a(n) = [ x^(n-1) ] (1+x+x^2+x^3+x^4)^n.

MAPLE

A135413 := proc(n) local ogf, i ; ogf := 1 ; for i from 1 to n do ogf := taylor(ogf*(1+x+x^2+x^3+x^4), x=0, n) ; od: coeftayl(ogf, x=0, n-1) ; end: seq(A135413(n), n=1..30) ; # R. J. Mathar, Apr 21 2008

CROSSREFS

For k=2 this is A005717, for k=3 this is A005726.

Sequence in context: A150124 A045631 A229472 * A193653 A147748 A150125

Adjacent sequences:  A135410 A135411 A135412 * A135414 A135415 A135416

KEYWORD

nonn,easy

AUTHOR

Andrey Bovykin (indiscernibles(AT)googlemail.com), Mar 01 2008

EXTENSIONS

More terms from R. J. Mathar, Apr 21 2008

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified August 28 10:58 EDT 2015. Contains 261120 sequences.