A211478 Number of -1..1 arrays x(i) of n+1 elements i=1..n+1 with x(i)+x(j), x(i+1)+x(j+1), -(x(i)+x(j+1)), and -(x(i+1)+x(j)) having one, two or three distinct values for every i<=n and j<=n.

9, 23, 59, 145, 351, 835, 1971, 4625, 10831, 25349, 59387, 139365, 327791, 772867, 1826897, 4329065, 10282271, 24474781, 58370829, 139453231, 333678255, 799483191, 1917764183, 4604847317, 11066414301, 26614313429, 64046049399

Offset

1,1

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 15*a(n-2) + a(n-3) + 33*a(n-4) - 28*a(n-5) - 12*a(n-6) + 16*a(n-7) + a(n-8) - 2*a(n-9).

Empirical g.f.: x*(9 - 40*x + 33*x^2 + 68*x^3 - 99*x^4 - 13*x^5 + 51*x^6 + x^7 - 6*x^8) / ((1 - x)*(1 - 2*x)*(1 - x - x^2)*(1 - 2*x - x^2)*(1 - x - 2*x^2 + x^3)). - Colin Barker, Jul 18 2018

Example

Some solutions for n=5:
..0....1....0....0....1...-1....0....1....1....0....1...-1....1....0....1...-1
.-1...-1....0....1....0....0....0...-1...-1...-1....1....0....0....1....0....0
..0....0...-1...-1...-1....1....1....0...-1....1....1....0....0....0....1...-1
.-1....0....0....0....0....0...-1....0...-1....1...-1....0....1...-1....0....1
..0....0...-1....1....0...-1...-1....0...-1....1....0....1....0....0....0....1
..0...-1....0...-1...-1....1...-1....0...-1....1...-1....0....1...-1....0...-1

Crossrefs

Sequence in context: A079040 A183338 A212676 * A147420 A259170 A057453

Adjacent sequences: A211475 A211476 A211477 * A211479 A211480 A211481

Keyword

nonn

Author

R. H. Hardin, Apr 12 2012

Status

approved