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Search: id:A087540
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| A087540 |
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Let A(n) be the matrix in the group GL(n,2) such that for 1<=i,j<=n : A[i,j] = 1 if i+j = n+1 A[i,j] = 0 if i+j != n+1 . a(n) is the centralizer of A(n) in GL(n,2). |
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2
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OFFSET
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1,2
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COMMENT
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The formula was given by Derek Holt (mareg(AT)mimosa.csv.warwick.ac.uk) in this thread from sci.math : http://mathforum.org/discuss/sci.math/t/538859.
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FORMULA
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for even n = 2m : a(n) = 2^(m^2) * |GL(m, 2)| = 2^(m^2) * A002884(m) . for odd n = 2m+1 : a(n) = 2^(m^2+2m) * |GL(m, 2)| = 2^(m^2+2m) * A002884(m).
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CROSSREFS
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Cf. A002884.
Sequence in context: A067964 A126429 A098272 this_sequence A052713 A136797 A009752
Adjacent sequences: A087537 A087538 A087539 this_sequence A087541 A087542 A087543
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KEYWORD
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nonn
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AUTHOR
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Yuval Dekel (dekelyuval(AT)hotmail.com), Oct 24 2003
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