A209604 Number of nX2 1..2 arrays with every element value z a city block distance of exactly z from another element value z

1, 2, 11, 45, 170, 538, 1674, 5410, 18001, 60486, 202486, 674159, 2238695, 7433743, 24704751, 82150290, 273210105, 908536081, 3020918528, 10044214676, 33396046046, 111040661940, 369210326847, 1227626858414, 4081857794878

Offset

1,2

Comments

Column 2 of A209610

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 3*a(n-1) +5*a(n-4) +16*a(n-5) +23*a(n-6) +6*a(n-7) -6*a(n-8) -21*a(n-9) -8*a(n-10) -9*a(n-11) -5*a(n-12) -4*a(n-13) +a(n-15) for n>16

Example

Some solutions for n=4
..2..2....2..2....2..2....1..2....2..2....1..1....1..1....1..2....2..1....1..2
..2..1....2..2....1..2....1..2....2..1....1..1....1..2....1..2....2..1....1..2
..2..1....2..2....1..2....1..2....2..1....2..2....2..1....2..2....2..2....1..2
..1..1....2..2....2..2....1..2....2..2....2..2....1..1....2..2....1..1....2..2

Crossrefs

Sequence in context: A127109 A054208 A257066 * A120279 A037751 A037639

Adjacent sequences: A209601 A209602 A209603 * A209605 A209606 A209607

Keyword

nonn

Author

R. H. Hardin Mar 10 2012

Status

approved