A189944 1/4 the number of arrangements of n+1 nonzero numbers x(i) in -2..2 with the sum of sign(x(i))*(|x(i)| mod x(i+1)) equal to zero

3, 8, 22, 72, 280, 1152, 4632, 17888, 67232, 251136, 947136, 3625216, 14033664, 54599680, 212521344, 826308096, 3211280896, 12490338304, 48666153984, 189986959360, 742894424064, 2908269379584, 11394480500736, 44672464896000

Offset

1,1

Comments

Column 2 of A189951

Links

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

Formula

Empirical: (n+1)*a(n) = 4*(2*n+1)*a(n-1) - 24*n*a(n-2) + 16*(2*n-1)*a(n-3). - Vaclav Kotesovec, Oct 19 2012

Example

Some solutions with n=3
..2....2....2....1...-2...-2....1....2....2....1....2...-2...-2...-2...-1...-2
..2....2....2....2....2...-2...-2....2...-2....1....2....2....2...-2....2...-2
..2...-2...-2...-1...-1....1...-1...-1....2...-1...-2....2...-1....2....1...-1
..2...-1...-2....2....1....1....2....1...-2...-1....2...-2...-1....1....2...-1

Crossrefs

Sequence in context: A233449 A148770 A369791 * A148771 A361866 A148772

Adjacent sequences: A189941 A189942 A189943 * A189945 A189946 A189947

Keyword

nonn

Author

R. H. Hardin May 02 2011

Status

approved