A123831 - OEIS

A123831

Number of ways to build a contiguous building with n LEGO blocks of size 2 X 4 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.

%I #9 Nov 29 2017 03:39:31

%S 2,24,88,1079,5563,74597,412309,5633649

%N Number of ways to build a contiguous building with n LEGO blocks of size 2 X 4 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.

%C The base block is not counted among the n and must be the only block in the bottom layer of the building.

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

%K nonn,more

%O 1,1

%A _Søren Eilers_, Oct 29 2006