Let G be a simple labeled graph with vertex set [n] and let P be a set partition of [n]. Then a(n) is the number of ordered pairs (G,P) such that for all x,y in [n], if x and y are in the same block of P then there is a path in G from x to y.

A371126

Let G be a simple labeled graph with vertex set [n] and let P be a set partition of [n]. Then a(n) is the number of ordered pairs (G,P) such that for all x,y in [n], if x and y are in the same block of P then there is a path in G from x to y.