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%I #12 Sep 12 2018 05:29:55
%S 1,1,3,4,16,24,103,163,721,1173,5283,8783,39912,67381,308314,526553,
%T 2421040,4172834,19257309,33438244,154761065,270372085
%N 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 Cf. A112389, A123762 - A123827, A123829 - A123849.
%K nonn,more
%O 1,3
%A _Søren Eilers_, Oct 29 2006
%E More terms by _Søren Eilers_, Sep 12 2018
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