A193696 Number of arrays of -2..2 integers x(1..n) with every x(i) in a subsequence of length 1, 2 or 3 with sum zero

1, 5, 23, 83, 299, 1081, 3931, 14293, 51955, 188859, 686519, 2495537, 9071325, 32974351, 119862177, 435700975, 1583780905, 5757072535, 20927062737, 76070247573, 276516705575, 1005143149813, 3653713262601, 13281312856865

Offset

1,2

Comments

Column 2 of A193702

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = 3*a(n-1) +2*a(n-2) -2*a(n-3) +5*a(n-4) +16*a(n-5) +18*a(n-6) +20*a(n-7) +23*a(n-8) +18*a(n-9) +7*a(n-10) +a(n-11) +4*a(n-12) +7*a(n-13) +a(n-14) -7*a(n-15) -8*a(n-16) -4*a(n-17) -a(n-18)

Example

Some solutions for n=6
.-1....0....1...-2...-1...-2....2...-1...-1....0....1....0...-1...-1...-2....1
..0...-1....0....0....1....2....0...-1....2....1...-1....1....1...-1....0...-1
..1....1...-1....2...-1...-2...-2....2...-1...-1....0....1....1....2....2....2
..1...-1....0...-1....1....1....1....0...-1...-2....2...-2...-2....1...-1...-2
.-1...-2....1...-1...-2...-1....1....1...-2....1...-1...-1....1....0....1...-1
..1....2....0....2....2....1...-2...-1....2....1...-1....1....0...-1...-1....1

Crossrefs

Sequence in context: A113946 A283114 A290938 * A377496 A147359 A034447

Adjacent sequences: A193693 A193694 A193695 * A193697 A193698 A193699

Keyword

nonn

Author

R. H. Hardin Aug 02 2011

Status

approved