A324263 -id:A324263

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A324244

Triangle read by rows: T(n,k) is the number of connected graphs on n nodes with k peripheral nodes.

+0
3

1, 0, 1, 0, 1, 1, 0, 2, 2, 2, 0, 5, 4, 7, 5, 0, 25, 20, 16, 23, 28, 0, 185, 146, 119, 57, 123, 223, 0, 2459, 1728, 1523, 948, 405, 903, 3151, 0, 58156, 36109, 32119, 24637, 13927, 4713, 11746, 79673, 0, 2617378, 1446609, 1304109, 1026845, 723871, 353620, 110734, 279535, 3853870

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

1,8

COMMENTS

The peripheral nodes of a graph are those with eccentricity equal to the diameter.

LINKS

Table of n, a(n) for n=1..55.

Eric Weisstein's World of Mathematics, Graph Periphery

Wikipedia, Distance (graph theory)

EXAMPLE

Triangle begins:

0, 1;

0, 1, 1;

0, 2, 2, 2;

0, 5, 4, 7, 5;

0, 25, 20, 16, 23, 28;

0, 185, 146, 119, 57, 123, 223;

0, 2459, 1728, 1523, 948, 405, 903, 3151;

0, 58156, 36109, 32119, 24637, 13927, 4713, 11746, 79673;

...

CROSSREFS

Row sums give A001349.

Column k=2 is A324263.

Rightmost diagonal is A324264.

Cf. A294522, A294525, A324239.

KEYWORD

nonn,tabl

AUTHOR

Andrew Howroyd, Sep 02 2019

STATUS

approved

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