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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A298422 Number of rooted trees with n nodes in which all positive outdegrees are the same. 44
1, 1, 2, 2, 3, 2, 5, 2, 6, 4, 9, 2, 20, 2, 26, 12, 53, 2, 120, 2, 223, 43, 454, 2, 1100, 11, 2182, 215, 4902, 2, 11446, 2, 24744, 1242, 56014, 58, 131258, 2, 293550, 7643, 676928, 2, 1582686, 2, 3627780, 49155, 8436382, 2, 19809464, 50, 46027323, 321202 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Row sums of A298426.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..200

FORMULA

a(n) = 2 <=> n in {A008864}. - Alois P. Heinz, Jan 20 2018

EXAMPLE

The a(9) = 6 trees: ((((((((o)))))))), (o(o(o(oo)))), (o((oo)(oo))), ((oo)(o(oo))), (ooo(oooo)), (oooooooo).

MATHEMATICA

srut[n_]:=srut[n]=If[n===1, {{}}, Select[Join@@Function[c, Union[Sort/@Tuples[srut/@c]]]/@Select[IntegerPartitions[n-1], Function[ptn, And@@(Divisible[#-1, Length[ptn]]&/@ptn)]], SameQ@@Length/@Cases[#, {__}, {0, Infinity}]&]];

Table[srut[n]//Length, {n, 20}]

CROSSREFS

Cf. A000005, A000081, A000598, A001190, A001678, A003238, A004111, A008864, A032305, A067538, A111299, A124343, A143773, A289078, A289079, A295461, A298118, A298204, A298423, A298424, A298426.

Sequence in context: A115119 A066656 A164896 * A304716 A237984 A118136

Adjacent sequences:  A298419 A298420 A298421 * A298423 A298424 A298425

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jan 19 2018

EXTENSIONS

a(44)-a(52) from Alois P. Heinz, Jan 20 2018

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 19 08:14 EDT 2019. Contains 326115 sequences. (Running on oeis4.)