OFFSET
1,2
COMMENTS
Necessarily A has all 1's on the main diagonal.
A real matrix M is positive semi-definite if its eigenvalues are >= 0.
For n <= 4, a(n) equals the upper bound 3^C(n,2).
For the number of different values of symmetric parts A + A', see A085658. - Max Alekseyev, Nov 11 2006
FORMULA
a(n) = Sum_{k=0..C(n,2)} 2^k * A083029(n,k).
CROSSREFS
KEYWORD
nonn,more,nice
AUTHOR
N. J. A. Sloane, Jul 13 2003
EXTENSIONS
Definition corrected Nov 10 2006
a(6)-a(8) from Max Alekseyev, Nov 11 2006
Edited by Max Alekseyev, Jun 05 2024
STATUS
approved