A083402 Let A_n be the upper triangular matrix in the group GL(n,2) that has zero entries below the main diagonal and 1 elsewhere; a(n) is the size of the conjugacy class of this matrix in GL(n,2).

1, 3, 42, 2520, 624960, 629959680, 2560156139520, 41781748196966400, 2732860586067178291200, 715703393163961188325785600, 750102961052993818881476159078400, 3145391744524297920839316348340273152000, 52764474940208177704130232748554603290689536000

Offset

1,2

Links

Eric M. Schmidt, Table of n, a(n) for n = 1..30

Formula

a(n) = A002884(n) / 2^(n-1).

Example

For example for n=4 the matrix is / 1,1,1,1 / 0,1,1,1 / 0,0,1,1 / 0,0,0,1 /.

Maple

a:= n-> 2^((n-1)*(n-2)/2) *mul(2^k-1, k=1..n):
seq(a(n), n=1..15);  # Alois P. Heinz, May 14 2013

Mathematica

a[n_] := 2^((n-1)*(n-2)/2)*Product[2^k-1, {k, 1, n}]; Table[a[n], {n, 1, 15}] (* Jean-François Alcover, Feb 17 2014, after Alois P. Heinz *)

Crossrefs

Cf. A002884, A070731, A082877, A062383.

Sequence in context: A331705 A156108 A210929 * A145984 A213956 A157552

Adjacent sequences: A083399 A083400 A083401 * A083403 A083404 A083405

Keyword

nonn

Author

Yuval Dekel (dekelyuval(AT)hotmail.com), Jun 12 2003

Extensions

More terms from Eric M. Schmidt, May 14 2013

Status

approved