%I #8 Dec 11 2020 08:03:26
%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