181955

Appears in sequences

• Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 3 which is symmetric after a rotation by 180 degrees.at n=7A123825
• Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-1)*b(n), where a(0) = 1, a(1) = 3, b(0) = 2, b(1) = 4, b(2) = 5, and (a(n)) and (b(n)) are increasing complementary sequences.at n=18A296273