A123825 - OEIS

%I #5 Oct 09 2013 14:20:53

%S 1,1,25,53,1189,2947,66094,181955,3979943

%N Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2x3 which is symmetric after a rotation by 180 degrees.

%Y Cf. A112389, A123762 - A123827, A123829 - A123849.

%K nonn

%O 1,3

%A _Søren Eilers_, Oct 29 2006