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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. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 12 2012
STATUS
approved

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Last modified June 18 12:25 EDT 2024. Contains 373481 sequences. (Running on oeis4.)