A351052 Number of unlabeled digraphs with n nodes containing a global sink (or source), self-loops allowed.

1, 2, 18, 440, 32404, 7423456, 5473328160, 13430706072192, 113086387825668384, 3345639802029563258880, 353900830082830194441001984, 135600928084762756427776332541952, 190092581374833963606044859875698932736, 982736440685354936080688846774429648871161856

Offset

1,2

Links

Table of n, a(n) for n=1..14.

Jim Snyder-Grant, C code to generate and count digraphs with global sinks

Eric Weisstein's World of Mathematics, Digraph Sink

Example

For n=3, 18 digraph edge-sets (vertex 0 is the single global sink):
  {21,10}
  {20,10}
  {22,21,10}
  {22,20,10}
  {21,12,10}
  {21,11,10}
  {20,12,10}
  {22,21,12,10}
  {22,21,11,10}
  {22,20,12,10}
  {22,20,11,10}
  {21,20,12,10}
  {21,12,11,10}
  {20,11,12,10}
  {22,21,20,12,10}
  {22,21,12,11,10}
  {22,20,12,11,10}
  {22,21,20,12,11,10}.

Prog

(C) \\ See Jim Snyder-Grant C code to generate and count digraphs with global sinks ./gsinks -l
(PARI) \\ See PARI link in A350794 for program code.
seq(n)={Vec(InitiallyV(GraphCIData(n, DigraphWithLoopEdges)))} \\ Andrew Howroyd, Jan 30 2022

Crossrefs

Cf. A350360 (self-loops not allowed).

Sequence in context: A201732 A260656 A141074 * A082402 A208055 A306655

Adjacent sequences: A351049 A351050 A351051 * A351053 A351054 A351055

Keyword

nonn

Author

Jim Snyder-Grant, Jan 30 2022

Extensions

Terms a(8) and beyond from Andrew Howroyd, Jan 30 2022

Status

approved