A087785 Number of elements in GL(2,Z_n) x with x^2 == -I mod n where I is the identity matrix.

1, 4, 6, 12, 32, 24, 42, 48, 54, 128, 110, 72, 184, 168, 192, 192, 308, 216, 342, 384, 252, 440, 506, 288, 752, 736, 486, 504, 872, 768, 930, 768, 660, 1232, 1344, 648, 1408, 1368, 1104, 1536, 1724, 1008, 1806, 1320, 1728, 2024, 2162, 1152, 2058, 3008, 1848

Offset: 1

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Oct 06 2003

Keywords

• mult
• nonn

Crossrefs

Cf. A066907, A000089.

Extensions

More terms from David Wasserman, Jun 17 2005