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A066514
Number of subgroups of the group GL(2,Z_n) of invertible 2 X 2 matrices mod n (sequence A000252).
2
1, 6, 55, 234, 466, 758, 1704, 24587, 6656, 6718, 6428, 114210, 17158, 26180, 135869, 701426, 33277, 126920, 52320, 1341656, 469872, 87924, 48976, 50257306, 140918, 291060, 348528, 3952920, 175438, 3685062, 285952, 12024029, 1657948, 567994, 4624192, 15262640, 539046, 838096
OFFSET
1,2
PROG
(GAP) c := CyclicGroup(n); aut := AutomorphismGroup(DirectProduct(c, c)); lat := LatticeSubgroups(aut);
(Magma) [&+[s`length : s in Subgroups(GL(2, ResidueClassRing(n)))] : n in [2..10]]; // Robin Visser, Aug 09 2023
CROSSREFS
Cf. A000252.
Sequence in context: A069508 A079465 A061792 * A281075 A009577 A097300
KEYWORD
nonn
AUTHOR
Sharon Sela (sharonsela(AT)hotmail.com), Jan 04 2002
EXTENSIONS
a(7)-a(11) from Andrew Howroyd, Jul 02 2018
More terms from Robin Visser, Aug 09 2023
STATUS
approved