A296621 Number of 5-regular (quintic) connected graphs on 2*n nodes with diameter k written as irregular triangle T(n,k).

1, 0, 3, 0, 60, 0, 5457, 2391, 0, 258474, 3200871, 37, 1, 0, 1041762, 2583730089, 364670, 154, 0

Offset

3,3

Comments

The results were found by applying the Floyd-Warshall algorithm to the output of Markus Meringer's GenReg program.

Links

Table of n, a(n) for n=3..21.

M. Meringer, GenReg, Generation of regular graphs.

Wikipedia, Distance (graph theory).

Wikipedia, Floyd-Warshall algorithm.

Example

Triangle begins:
                     Diameter
   n/ 1       2          3      4   5
   6: 0       1
   8: 0       3
  10: 0      60
  12: 0    5457       2391
  14: 0  258474    3200871     37   1
  16: 0 1041762 2583730089 364670 154
.
The adjacency matrix of the unique 5-regular graph on 14 nodes with diameter 5 is provided as example in A296526.

Crossrefs

Cf. A006821 (row sums), A068934, A204329, A296525 (number of terms in each row), A296526, A296620.

Sequence in context: A271762 A264882 A012759 * A120953 A009784 A276909

Adjacent sequences: A296618 A296619 A296620 * A296622 A296623 A296624

Keyword

nonn,tabf,more

Author

Hugo Pfoertner, Dec 19 2017

Status

approved