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 A251421 Number of length n+2 0..1 arrays with the sum of the maximum minus twice the median plus the minimum of adjacent triples multiplied by some arrangement of +-1 equal to zero. 2
 2, 12, 12, 40, 56, 144, 240, 544, 992, 2112, 4032, 8320, 16256, 33024, 65280, 131584, 261632, 525312, 1047552, 2099200, 4192256, 8392704, 16773120, 33562624, 67100672, 134234112, 268419072, 536903680, 1073709056, 2147549184, 4294901760 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A251428. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 2*a(n-1) +2*a(n-2) -4*a(n-3). Conjectures from Colin Barker, Mar 20 2018: (Start) G.f.: 2*x*(1 + 4*x - 8*x^2) / ((1 - 2*x)*(1 - 2*x^2)). a(n) = 2*(2^(n/2) + 2^n) for n even. a(n) = 2*(2^n - 2^((n-3)/2+1)) for n odd. (End) EXAMPLE Some solutions for n=10: ..1....0....1....1....0....0....0....1....1....0....1....1....1....0....1....0 ..0....1....1....0....1....1....1....0....0....1....0....1....1....1....0....0 ..0....1....1....0....1....0....0....0....1....0....0....1....1....0....0....1 ..0....1....0....0....1....0....0....1....0....1....1....1....1....0....1....1 ..1....1....1....1....1....0....1....0....0....0....0....0....0....1....0....0 ..1....1....0....1....1....0....1....0....1....0....1....1....0....0....0....1 ..0....1....0....0....0....0....0....1....0....1....0....0....1....0....0....0 ..1....1....0....0....0....1....0....1....0....0....1....0....1....1....0....1 ..1....1....0....1....0....0....0....0....1....1....0....0....0....1....0....1 ..1....1....0....0....0....0....0....0....0....0....0....0....1....0....0....0 ..0....1....1....0....0....0....1....1....1....1....1....0....1....1....1....1 ..0....0....1....0....1....1....0....0....1....1....0....0....0....1....0....0 CROSSREFS Cf. A251428. Sequence in context: A088240 A168457 A045895 * A226393 A371375 A198532 Adjacent sequences: A251418 A251419 A251420 * A251422 A251423 A251424 KEYWORD nonn AUTHOR R. H. Hardin, Dec 02 2014 STATUS approved

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Last modified August 2 19:53 EDT 2024. Contains 374875 sequences. (Running on oeis4.)