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A248432
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Number of length n+2 0..7 arrays with every three consecutive terms having the sum of some two elements equal to twice the third.
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1
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80, 140, 252, 462, 884, 1684, 3200, 6216, 11944, 22810, 44396, 85402, 163204, 317716, 611248, 1168198, 2274196, 4375320, 8362052, 16278784, 31318664, 59855842, 116523764, 224179214, 428448488, 834077068, 1604674164, 3066832822
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) + 10*a(n-3) - 10*a(n-4) - 22*a(n-6) + 22*a(n-7) + 12*a(n-9) - 12*a(n-10) - a(n-12) + a(n-13).
Empirical g.f.: 2*x*(40 + 30*x + 56*x^2 - 295*x^3 - 89*x^4 - 160*x^5 + 588*x^6 + 58*x^7 + 96*x^8 - 317*x^9 - 5*x^10 - 9*x^11 + 27*x^12) / ((1 - x)*(1 - 10*x^3 + 22*x^6 - 12*x^9 + x^12)). - Colin Barker, Nov 08 2018
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EXAMPLE
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Some solutions for n=6:
..6....6....0....4....2....3....4....6....4....3....2....4....5....2....3....4
..4....2....3....2....3....1....6....4....2....5....3....2....3....4....5....5
..5....4....6....0....4....2....5....5....3....4....1....6....7....3....7....3
..3....0....0....4....5....0....4....3....1....6....5....4....5....5....6....7
..7....2....3....2....3....1....3....1....2....2....3....5....3....4....5....5
..5....4....6....3....7....2....2....2....0....4....7....3....4....3....7....6
..3....6....0....1....5....0....4....0....1....3....5....1....5....5....3....4
..1....5....3....5....6....1....3....1....2....2....3....5....6....4....5....2
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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