|
Search: id:A086812
|
|
|
| A086812 |
|
Number of symmetric invertible n X n matrices over GF(2). |
|
+0
2
|
|
| 1, 4, 28, 448, 13888, 888832, 112881664, 28897705984, 14766727757824, 15121129224011776, 30952951521552105472, 126783289432277424013312, 1038481923739784380093038592, 17014487838552627283444344291328
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
REFERENCES
|
R. P. Brent and B. D. McKay, Determinants of random symmetric matrices over Zm, Ars Combinatoria, 26-A (1988) 57-64.
|
|
LINKS
|
R. P. Brent and B. D. McKay, Determinants of random symmetric matrices over Zm
|
|
FORMULA
|
Let k = ceil(n/2). Then a(n) = 2^(n*(n+1)/2) * product j=1..2k (1-(1/2)^j) / product j=1..k (1-(1/4)^j)
|
|
MAPLE
|
for n from 1 to 31 do k := ceil(n/2); a[n] := 2^(n*(n+1)/2)*product(1-(1/2)^j, j=1..2*k)/product(1-(1/4)^j, j=1..k); od:seq(a[j], j=1..31); (from Sascha Kurz)
|
|
CROSSREFS
|
Cf. A002884.
Sequence in context: A140425 A095288 A132685 this_sequence A111817 A134048 A091969
Adjacent sequences: A086809 A086810 A086811 this_sequence A086813 A086814 A086815
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 15 2003
|
|
EXTENSIONS
|
More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net) and Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Sep 19 2003
|
|
|
Search completed in 0.002 seconds
|
