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

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

Crossrefs

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

Row sums give A001349.

Sequence in context: A099064 A280398 A052422 * A011218 A171244 A028305

Adjacent sequences: A294522 A294523 A294524 * A294526 A294527 A294528

Keyword

nonn,tabl

Author

Andrew Howroyd, Nov 01 2017

Status

approved