A294525 Triangle read by rows: T(n,k) is the number of simple 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

Offset: 1

Author

Andrew Howroyd, Nov 01 2017

Keywords

• nonn
• tabl

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.

Examples

			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;
: 1463, 821, 1055, 1426, 1390, 1811,   0, 3151;
...
		

Links

• Sean A. Irvine, Table of n, a(n) for n = 1..78
• Eric Weisstein's World of Mathematics, Graph Center

Crossrefs

Columns 1..5 except first term are A052437, A052438, A052439, A052440, A052441.

Row sums give A001349.