A066541 Number of normal subgroups of the group GL(2,Z_n) of invertible 2 X 2 matrices mod n (sequence A000252).

1, 3, 5, 12, 6, 17, 8, 46, 14, 22, 8, 82, 12, 28, 38, 112, 10, 48, 12, 116, 48, 28, 8, 386, 18, 44, 27, 140, 12, 162, 16, 232, 48, 38, 64, 234, 18, 42, 76, 596, 16, 196, 16, 140, 108, 28, 8, 1022, 24, 66, 66, 232, 12, 93, 64, 680, 72, 44, 8, 1032, 24, 56, 204

Offset

1,2

Links

Andrew Howroyd, Table of n, a(n) for n = 1..100

Prog

(GAP) Concatenation([1], List([2..20], n->Size(NormalSubgroups(GL(2, Integers mod n))))); # Andrew Howroyd, Jul 04 2018

Crossrefs

Cf. A000252, A066514, A316498.

Sequence in context: A281087 A101315 A343738 * A279728 A087122 A358336

Adjacent sequences: A066538 A066539 A066540 * A066542 A066543 A066544

Keyword

nonn

Author

Sharon Sela (sharonsela(AT)hotmail.com), Jan 07 2002

Extensions

Terms a(16) and beyond from Andrew Howroyd, Jul 04 2018

Status

approved