A203840 Number of n X 2 0..3 arrays with every nonzero element less than or equal to at least two horizontal and vertical neighbors.

1, 4, 16, 50, 184, 810, 3502, 14751, 63204, 274824, 1195748, 5201911, 22685592, 99123373, 433452835, 1896510229, 8302931200, 36367291798, 159341158550, 698313973844, 3060976848490, 13419502926856, 58838771883237

Offset

1,2

Comments

Column 2 of A203846.

Links

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

Formula

Empirical: a(n) = 10*a(n-1) -39*a(n-2) +104*a(n-3) -251*a(n-4) +391*a(n-5) -483*a(n-6) +687*a(n-7) -378*a(n-8) +503*a(n-9) -247*a(n-10) -66*a(n-11) -292*a(n-12) -300*a(n-13) -217*a(n-14) -153*a(n-15) -70*a(n-16) -27*a(n-17) -8*a(n-18) -a(n-19).

Example

Some solutions for n=4
..3..3....1..1....2..2....3..3....3..3....1..1....1..1....2..2....0..0....0..0
..3..3....2..2....2..2....3..3....3..3....1..1....3..3....3..3....2..2....0..0
..1..1....2..2....0..0....1..1....1..1....2..2....3..3....3..3....2..2....0..0
..0..0....0..0....0..0....0..0....0..0....2..2....0..0....3..3....0..0....0..0

Crossrefs

Cf. A203846.

Sequence in context: A298173 A323932 A121184 * A089093 A316321 A058234

Adjacent sequences: A203837 A203838 A203839 * A203841 A203842 A203843

Keyword

nonn

Author

R. H. Hardin, Jan 06 2012

Status

approved