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A066541 Number of normal subgroups of the group GL(2,Z_n) of invertible 2 X 2 matrices mod n (sequence A000252). 2
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 (list; graph; refs; listen; history; text; internal format)
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 A320433 * A279728 A087122 A286900

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

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Last modified April 6 11:51 EDT 2020. Contains 333273 sequences. (Running on oeis4.)