%I

%S 81,321,825,1689,2601,4185,5529,8145,10401,13137

%N Number of 3 X 3 integer matrices with elements in the range [ -n,n ] which represent a rotation of order 2.

%F A053170(n) = 2 * (1 + a(n) + A053172(n) + A053173(n) + A053174(n)).

%Y Cf. A053170, A053172, A053173, A053174.

%K nonn,more

%O 1,1

%A _Ralf W. Grosse-Kunstleve_, Mar 26 2000