A063379 Number of orbits of the group of units of Z/(n) acting naturally on the 2-subsets of Z/(n).

1, 2, 4, 3, 9, 4, 11, 8, 13, 6, 25, 7, 17, 18, 24, 9, 33, 10, 35, 23, 25, 12, 59, 18, 29, 26, 45, 15, 71, 16, 49, 33, 37, 32, 86, 19, 41, 38, 81, 21, 91, 22, 65, 61, 49, 24, 123, 32, 73, 48, 75, 27, 105, 46, 103, 53, 61, 30, 181, 31, 65, 78, 98, 53, 131, 34

Offset: 2

Author

W. Edwin Clark, Jul 15 2001

Keywords

• nonn

Examples

			a(3) = 2 since when U(3) = {1,2} acts naturally on the three 2-subsets {0,1}, {0,2}, {1,2} of Z/(3) the orbits are {{0,1},{0,2}} and {{1,2}}. Note that 2{0,1} = {0,2} but there is no unit a in U(3) such that a{0,1} = {1,2}.
		

Crossrefs

Cf. A065957, A063381, A000005, A056376 + 1, A056371 - 1

Extensions

More terms from Sean A. Irvine, Apr 22 2023