A324163 Triangle read by rows: T(n,k) is the number of connected k-regular simple graphs on n labeled vertices, (0 <= k < n).

1, 0, 1, 0, 0, 1, 0, 0, 3, 1, 0, 0, 12, 0, 1, 0, 0, 60, 70, 15, 1, 0, 0, 360, 0, 465, 0, 1, 0, 0, 2520, 19320, 19355, 3507, 105, 1, 0, 0, 20160, 0, 1024380, 0, 30016, 0, 1, 0, 0, 181440, 11166120, 66462480, 66462606, 11180820, 286884, 945, 1

Offset

1,9

Links

Andrew Howroyd, Table of n, a(n) for n = 1..210

Formula

Column k is the logarithmic transform of column k of A059441.

Example

Triangle begins:
  1;
  0, 1;
  0, 0,     1;
  0, 0,     3,     1;
  0, 0,    12,     0,       1;
  0, 0,    60,    70,      15,    1;
  0, 0,   360,     0,     465,    0,     1;
  0, 0,  2520, 19320,   19355, 3507,   105, 1;
  0, 0, 20160,     0, 1024380,    0, 30016, 0, 1;
  ...

Crossrefs

Column k=2 is A001710(n-1) for n >= 3.

Column k=3 is aerated A004109.

Column k=4 is A272905.

Row sums are A322659.

Cf. A059441 (not necessarily connected), A068934 (unlabeled).

Sequence in context: A034370 A144402 A264429 * A127537 A265314 A364207

Adjacent sequences: A324160 A324161 A324162 * A324164 A324165 A324166

Keyword

nonn,tabl

Author

Andrew Howroyd, Sep 02 2019

Status

approved