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Number of ways to build a contiguous building with n LEGO blocks of size 1 X 4 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position.
0

%I #8 Jul 21 2017 13:27:10

%S 7,55,511,5000,51674,547204,5940045,65472189,731569499,8258444996,

%T 94045306573

%N Number of ways to build a contiguous building with n LEGO blocks of size 1 X 4 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position.

%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,hard

%O 1,1

%A _Søren Eilers_, Oct 29 2006