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