A223187 - OEIS

A223187

Number of n X n 0..2 arrays with all rows and columns having a nonnegative second derivative in a quadratic least squares fit, with one and two element arrays taken as having a zero second derivative.

%I #7 Apr 16 2024 22:44:38

%S 3,81,1138,1133664,3815358480,103879396217927,36869649918720635277

%N Number of n X n 0..2 arrays with all rows and columns having a nonnegative second derivative in a quadratic least squares fit, with one and two element arrays taken as having a zero second derivative.

%C Diagonal of A223195.

%e Some solutions for n=3

%e ..2..2..2....0..0..0....1..0..1....1..0..0....2..0..2....2..1..1....2..0..2

%e ..1..0..0....1..0..0....1..0..1....1..0..1....2..0..1....2..0..1....1..0..1

%e ..0..0..0....2..0..1....1..0..2....2..2..2....2..2..2....2..0..1....2..0..1

%Y Cf. A223195.

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 18 2013