183340

Appears in sequences

• Number of n X 1 1..3 arrays with no element with value z exactly a city block distance of z from another element with value z.at n=18A209367
• a(0) = 0 by convention; for n>0, a(n) is the number of edges in the n-th figure shown in A255011 (meaning the figure with 4n points on the perimeter).at n=11A331448