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Search: id:A028361
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| A028361 |
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Totally isotropic spaces of index n in orthogonal geometry of dimension 2n. |
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+0
11
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| 1, 2, 6, 30, 270, 4590, 151470, 9845550, 1270075950, 326409519150, 167448083323950, 171634285407048750, 351678650799042888750, 1440827432323678715208750, 11804699153027899713705288750
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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These numbers appear in first column of A155103. [From Mats Granvik (mats.granvik(AT)abo.fi), Jan 20 2009]
Equals row sums of unsigned triangle A158474 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Mar 20 2009]
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REFERENCES
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C. Bachoc and P. Gaborit, On extremal additive F_4 codes of length 10 to 18, J. Theorie Nombres Bordeaux, 12 (2000), 255-271.
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..50
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FORMULA
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Product( 2^i+1, i=0..n-1) (n>0).
Asymptotic to C*2^(n*(n-1)/2) where C=4.76846205806274344829979857....=prod(k>=0, 1+1/2^k) - Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 09 2003
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CROSSREFS
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A028362.
Cf. A155103. [From Mats Granvik (mats.granvik(AT)abo.fi), Jan 20 2009]
Cf. A158474 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Mar 20 2009]
Sequence in context: A097385 A066068 A121406 this_sequence A106339 A120295 A071350
Adjacent sequences: A028358 A028359 A028360 this_sequence A028362 A028363 A028364
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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