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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
OFFSET
1,1
COMMENTS
Column 1 of A251428.
LINKS
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 02 2014
STATUS
approved