A200051 Number of -2..2 arrays x(0..n-1) of n elements with zero sum and elements alternately strictly increasing and strictly decreasing

1, 4, 10, 26, 68, 178, 472, 1276, 3462, 9496, 26024, 71956, 198740, 552814, 1535556, 4290252, 11968194, 33553214, 93917400, 264020106, 741024426, 2087799972, 5872999754, 16577458520, 46720454112, 132081262316, 372843051320

Offset

1,2

Comments

Column 2 of A200057

Links

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

Example

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

Crossrefs

Sequence in context: A218208 A207095 A126358 * A200663 A200464 A099234

Adjacent sequences: A200048 A200049 A200050 * A200052 A200053 A200054

Keyword

nonn

Author

R. H. Hardin Nov 13 2011

Status

approved