A294525 - OEIS

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A294525

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

1, 0, 1, 1, 0, 1, 2, 2, 0, 2, 8, 4, 4, 0, 5, 29, 19, 18, 18, 0, 28, 180, 84, 119, 118, 129, 0, 223, 1463, 821, 1055, 1426, 1390, 1811, 0, 3151, 20093, 12485, 17297, 24853, 29987, 30515, 46177, 0, 79673, 474063, 343572, 486446, 763319, 1015304, 1247381, 1296986, 2235630, 0, 3853870

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

OFFSET

1,7

COMMENTS

The column sequences A052437-A052441 also include disconnected graphs. Disconnected graphs have an infinite radius and all nodes are considered a part of the center.

LINKS

Sean A. Irvine, Table of n, a(n) for n = 1..78

Eric Weisstein's World of Mathematics, Graph Center

EXAMPLE

Triangle begins:

: 1;

: 0, 1;

: 1, 0, 1;

: 2, 2, 0, 2;

: 8, 4, 4, 0, 5;

: 29, 19, 18, 18, 0, 28;

: 180, 84, 119, 118, 129, 0, 223;