A123773 - cp's OEIS frontend

A123773 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 3 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.

%I A123773 #12 Sep 12 2018 05:29:55
%S A123773 1,1,3,4,16,24,103,163,721,1173,5283,8783,39912,67381,308314,526553,
%T A123773 2421040,4172834,19257309,33438244,154761065,270372085
%N A123773 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 3 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.
%Y A123773 Cf. A112389, A123762 - A123827, A123829 - A123849.
%K A123773 nonn,more
%O A123773 1,3
%A A123773 _Søren Eilers_, Oct 29 2006
%E A123773 More terms by _Søren Eilers_, Sep 12 2018

cp's OEIS Frontend

A123773 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 3 which is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees.