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A125586
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2^(2n-1) - (n+2)*3^(n-2).
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1
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1, 4, 17, 74, 323, 1400, 6005, 25478, 107015, 445556, 1841273, 7561922, 30897227, 125714672, 509767421, 2061390206, 8317305359, 33498803948, 134727010049, 541232563130, 2172291241811, 8712410196584, 34922863258757, 139921580805494, 560408087592983
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Number of n X n nonsingular real matrices with entries {0,1} in which the top left n-1 X n-1 submatrix is the identity matrix. See A125587 for proof.
The number of singular matrices is given by A006234.
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EXAMPLE
| a(2) = 4:
10 10 11 11
01 11 01 10
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CROSSREFS
| Cf. A125587, A006234.
Sequence in context: A018902 A095940 A184700 * A086351 A049027 A026751
Adjacent sequences: A125583 A125584 A125585 * A125587 A125588 A125589
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com) and Vinay Vaishampayan (vinay(AT)research.att.com), Jan 05 2007
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