Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two horizontal, vertical or antidiagonal neighbors.

A220682

Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two horizontal, vertical or antidiagonal neighbors.

Terms

    a(0) =1a(1) =4a(2) =94a(3) =15452a(4) =15978924a(5) =107713940118

External references