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Number of ways to build a contiguous building with n LEGO blocks of size 1 X 8 on top of a fixed block of the same size so that the building is symmetric after a rotation by 180 degrees.
0

%I #9 Nov 29 2017 03:38:01

%S 1,37,73,2995,9235,404559,1360441

%N Number of ways to build a contiguous building with n LEGO blocks of size 1 X 8 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 1,2

%A _Søren Eilers_, Oct 29 2006