A324239 Irregular triangle read by rows: T(n,k) is the number of simple connected graphs on n nodes with radius k, (0 <= k <= floor(n/2)).

1, 0, 1, 0, 2, 0, 4, 2, 0, 11, 10, 0, 34, 76, 2, 0, 156, 682, 15, 0, 1044, 9864, 207, 2, 0, 12346, 245518, 3197, 19, 0, 274668, 11366961, 74614, 326, 2

Offset

1,5

Links

Table of n, a(n) for n=1..35.

Eric Weisstein's World of Mathematics, Graph Radius

Wikipedia, Distance (graph theory)

Example

Triangle begins:
  1;
  0,      1;
  0,      2;
  0,      4,        2;
  0,     11,       10;
  0,     34,       76,     2;
  0,    156,      682,    15;
  0,   1044,     9864,   207,   2;
  0,  12346,   245518,  3197,  19;
  0, 274668, 11366961, 74614, 326, 2;
  ...

Crossrefs

Row sums give A001349.

Columns k=1..2 are A000088(n-1), A324061.

Cf. A283826, A294522, A294525, A324244.

Sequence in context: A373691 A339941 A211318 * A274706 A037035 A159984

Adjacent sequences: A324236 A324237 A324238 * A324240 A324241 A324242

Keyword

nonn,tabf,more

Author

Andrew Howroyd, Sep 02 2019

Status

approved