3,2

a(5) = 2 since when U(5) = {1,2,3,4} acts naturally on the five 4-subsets {0,1,2,3}, {0,1,2,4}, {0,1,3,4}, {0,2,3,4}, {1,2,3,4} of Z/(5) the orbits are {{0,1,2,3},{0,1,2,4}, {0,1,3,4}, {0,2,3,4}} and {{1,2,3,4}}.

Cf. A063379, A065957, A000005, A056376 + 1, A056371 - 1

Sequence in context: A013500 A021340 A121837 this_sequence A019078 A011071 A125124

Adjacent sequences: A063378 A063379 A063380 this_sequence A063382 A063383 A063384

nonn

W. Edwin Clark (eclark(AT)math.usf.edu), Jul 15 2001