A123805 - OEIS

A123805

Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 7 which is flat, i.e., with all blocks in parallel position, and symmetric after a rotation by 180 degrees.

%I #14 Sep 14 2018 03:51:23

%S 1,1,7,10,100,160,1688,2853,30903,53721,592395,1053025,11711448,

%T 21151575,236789391,432872895

%N Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 7 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

%O 1,3

%A _Søren Eilers_, Oct 29 2006

%E a(11)-a(16) from _Søren Eilers_, Sep 14 2018