A361588 Triangle read by rows: T(n,k) is the number of digraphs on n unlabeled nodes with k strongly connected components and without isolated nodes.

1, 0, 0, 0, 1, 1, 0, 5, 4, 4, 0, 83, 57, 37, 25, 0, 5048, 2411, 1110, 550, 271, 0, 1047008, 325015, 101467, 37140, 15024, 5682, 0, 705422362, 136887749, 27765860, 7139149, 2259378, 780314, 237684, 0, 1580348371788, 183852357683, 23088181536, 3923330808, 907186816, 258971872, 78716548, 20042357

Offset: 0

Author

Andrew Howroyd, Mar 16 2023

Keywords

• nonn
• tabl

Examples

			Triangle begins:
  1;
  0,       0;
  0,       1,      1;
  0,       5,      4,      4;
  0,      83,     57,     37,    25;
  0,    5048,   2411,   1110,   550,   271;
  0, 1047008, 325015, 101467, 37140, 15024, 5682;
  ...
		

Crossrefs

Column k=1 is A035512.

Main diagonal is A361589.

Row sums are A053598.

Cf. A350794, A361582, A361587, A361590.

Programs

PARI

\\ See PARI link in A350794 for program code.
{ my(A=A361588triang(6)); for(n=1, #A, print(A[n])) }

Formula

T(n,k) = A361582(n,k) - A361582(n-1,k-1).