An isolated point of a graph is a node of degree 0 (Hartsfield and Ringel 1990, p. 8; Harary 1994, p. 15; D'Angelo and West 2000, p. 212;
West 2000, p. 22). The number of -node graphs with no isolated points are 0, 1, 2, 7, 23, 122,
888, ... (OEIS A002494), the first few of which
are illustrated above. The number of graphical
partitions of length
is equal to the number of -node graphs that have no isolated points.