A127234 - OEIS

%I #7 May 08 2013 16:55:15

%S 1,2,36,17280,435456000,941525544960000,257498348545415577600000,

%T 12293098054744302855420641280000000,

%U 134988938425519353794787639744975077376000000000,434085115076654530026451920435442716425635693068288000000000000

%N a(n) = n! (sum(1..n-1))!.

%C Number of distinct n x n symmetrical matrices containing A000217(n+1) different elements which have that same trace.

%t Table[n! (Sum[x, {x, 1, n-1}])!, {n, 1, 10}]

%t Table[n!((n(n-1))/2)!,{n,10}] (* _Harvey P. Dale_, May 08 2013 *)

%Y Cf. A127233, A127235.

%K nonn

%O 1,2

%A _Artur Jasinski_, Jan 09 2007, Jan 11 2007

%E Edited by _Jason G. Wurtzel_, Oct 08 2010

%E Corrected and extended by _Harvey P. Dale_, May 08 2013