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

1,7

Links

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

Example

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.

Prog

(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

Crossrefs

Row sums give A051421.

Column sums give A350907.

The labeled version is A057274.

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

Sequence in context: A300269 A094225 A358641 * A258712 A238094 A140734

Adjacent sequences: A057274 A057275 A057276 * A057278 A057279 A057280

Keyword

nonn,tabf

Author

Vladeta Jovovic, Goran Kilibarda, Sep 14 2000

Extensions

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

Status

approved