One of Leon Hall's Erdos number = 3 chains:
Hall and Wagon, "Roads and wheels", Mathematics Magazine
71 (1998), 285-291
Baumgartner, Taylor, and Wagon, "On splitting stationary subsets of large cardinals", J. Symbolic Logic 42 (1997), no. 2, 203-214
Baumgartner, Erdos, and Higgs, "Colorful partitions of cardinal numbers", Canad. J. Math. 31 (1979), no. 3, 524-541
One of Leon Hall's Erdos number of 2nd kind = 4 chains:
Hall and Wagon, "Roads and wheels", Mathematics Magazine
71 (1998), 285-291
Wagon and Wilf, "When are subset sums equidistributed modulo m?", Electron. J. Combin. 1 (1994), Research Paper 3, approx 15 pp (electronic)
Odlyzko and Wilf, "Functional iteration and the Josephus problem", Glasgow Math. J. 33 (1991), no. 2, 235-240
Erdos and Odlyzko, "On the density of odd integers of the form $(p-1) 2\sp{-n}$ and related questions", J. Number Theory 11 (1979), no. 2, 257-263