A350449 Triangle read by rows: T(n,k) is the number of weakly connected acyclic digraphs on n unlabeled nodes with k arcs, n >= 1, k = 0..(n-1)*n/2.

1, 0, 1, 0, 0, 3, 1, 0, 0, 0, 8, 9, 6, 1, 0, 0, 0, 0, 27, 54, 79, 63, 33, 10, 1, 0, 0, 0, 0, 0, 91, 320, 732, 1136, 1281, 1056, 649, 281, 85, 15, 1, 0, 0, 0, 0, 0, 0, 350, 1788, 6012, 14378, 26529, 38407, 44621, 41638, 31321, 18843, 8983, 3325, 920, 180, 21, 1

Offset

1,6

Links

Andrew Howroyd, Table of n, a(n) for n = 1..1350 (rows 1..20)

Example

Triangle begins:
  [1] 1;
  [2] 0, 1;
  [3] 0, 0, 3, 1;
  [4] 0, 0, 0, 8,  9,  6,  1;
  [5] 0, 0, 0, 0, 27, 54, 79, 63, 33, 10, 1;
  ...

Prog

(PARI) \\ See PARI link in A122078 for program code.
{ my(T=WeakAcyclicDigraphsByArcs(6)); for(n=1, #T, print(T[n])) }

Crossrefs

Row sums are A101228.

Columns sums are A350451.

Leading diagonal is A000238.

Cf. A350447 (not necessarily connected), A350450 (transpose).

Sequence in context: A285118 A128208 A154721 * A185664 A300812 A144209

Adjacent sequences: A350446 A350447 A350448 * A350450 A350451 A350452

Keyword

nonn,tabf

Author

Andrew Howroyd, Dec 31 2021

Status

approved