A057277 Triangle T(n,k) of number of digraphs with a source on n unlabeled nodes with k arcs, k=0..n*(n-1).

1, 0, 1, 1, 0, 0, 2, 4, 4, 1, 1, 0, 0, 0, 4, 16, 34, 46, 38, 27, 13, 5, 1, 1, 0, 0, 0, 0, 9, 56, 229, 573, 1058, 1448, 1653, 1487, 1153, 707, 379, 154, 61, 16, 5, 1, 1, 0, 0, 0, 0, 0, 20, 198, 1218, 5089, 15596, 37302, 72776, 119531, 168233, 205923, 220337, 207147, 170965, 124099, 78811, 43861, 21209, 8951, 3242, 1043, 288, 76, 17, 5, 1, 1

Offset: 1

Author

Vladeta Jovovic, Goran Kilibarda, Sep 14 2000

Keywords

• nonn
• tabf

Examples

			Triangle begins:
  [1],
  [0, 1, 1],
  [0, 0, 2, 4, 4, 1, 1],
  [0, 0, 0, 4, 16, 34, 46, 38, 27, 13, 5, 1, 1],
  ....
The number of digraphs with a source on 3 unlabeled nodes is 12 = 2+4+4+1+1.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..2680 (rows 1..20)

Crossrefs

Row sums give A051421.

Column sums give A350907.

The labeled version is A057274.

Cf. A057270, A057276, A057278, A057279, A350794, A350797.

Programs

PARI

\\ See PARI link in A350794 for program code.
{ my(A=A057277triang(5)); for(n=1, #A, print(A[n])) } \\ Andrew Howroyd, Jan 21 2022

Extensions

Terms a(46) and beyond from Andrew Howroyd, Jan 21 2022