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 A211460 Number of -2..2 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 or three distinct values for every i<=n and j<=n. 1
 21, 53, 121, 259, 549, 1119, 2285, 4575, 9185, 18275, 36437, 72387, 144013, 286211, 569361, 1132703, 2254869, 4490887, 8948013, 17838815, 35573537, 70976563, 141639157, 282775411, 564615853, 1127756979, 2252749969, 4501187503 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 3*a(n-1) + 5*a(n-2) - 20*a(n-3) - 5*a(n-4) + 45*a(n-5) - 5*a(n-6) - 40*a(n-7) + 6*a(n-8) + 12*a(n-9). Empirical g.f.: x*(21 - 10*x - 143*x^2 + 51*x^3 + 332*x^4 - 83*x^5 - 312*x^6 + 60*x^7 + 104*x^8) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - x - x^2)*(1 - 2*x^2)*(1 - 3*x^2)). - Colin Barker, Jul 17 2018 EXAMPLE Some solutions for n=5: .-2....2....0....2...-1...-1....0...-2....2....2...-1....2....2....2...-1...-1 ..2...-2....0....0....1....0...-2....0....0...-2....0....0...-2....0....0....0 .-2....2...-1....0....0....1....0...-2....2....0....1...-2....0....0....0...-1 ..0....0....0....0....1....0...-2....0...-1....1....2....2....1...-1...-1...-2 .-2...-1....2....0...-1...-1....2...-2....2....0....1....0....0....0....0...-1 ..0....0....0...-1....1....0....0....0...-1....1....2...-2...-2...-1....2...-2 CROSSREFS Sequence in context: A280914 A304517 A007796 * A190664 A144302 A180674 Adjacent sequences:  A211457 A211458 A211459 * A211461 A211462 A211463 KEYWORD nonn AUTHOR R. H. Hardin, Apr 12 2012 STATUS approved

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Last modified October 22 19:53 EDT 2019. Contains 328319 sequences. (Running on oeis4.)