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A277795 Number of trees with n unlabeled nodes such that all nodes with degree >2 lie on a single path with length equal to the tree's diameter. 2
1, 1, 1, 1, 2, 3, 6, 11, 23, 47, 103, 223, 503, 1132, 2602, 5986, 13922, 32433, 75994, 178354, 419945, 990134, 2339033, 5531459 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

First differs from A000055 at a(10).

First differs from A130131 at a(10), n >= 1.

The ratio of consecutive terms seems to tend to some limit. - Andrey Zabolotskiy, Dec 12 2016

LINKS

Table of n, a(n) for n=0..23.

Andrey Zabolotskiy, Python script for the sequence

EXAMPLE

From Andrey Zabolotskiy, Nov 21 2016: (Start)

Three trees that are counted in A000055(10) but not in a(10):

(1)

o  o-o-o

|    |

o----o

|    |

o  o-o-o

(2)

o-o-o

  |

  o-o-o-o

  |

o-o-o

(3)

o-o-o-o-o-o-o

      |

    o-o-o

(End)

CROSSREFS

Cf. A000055, A130131.

Sequence in context: A274937 A199142 A090344 * A198662 A198620 A198648

Adjacent sequences:  A277792 A277793 A277794 * A277796 A277797 A277798

KEYWORD

nonn,more

AUTHOR

Gabriel Burns, Oct 31 2016

EXTENSIONS

Corrections and more terms from Andrey Zabolotskiy, Nov 21 2016

STATUS

approved

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Last modified October 20 23:39 EDT 2018. Contains 316405 sequences. (Running on oeis4.)