

A250381


Number of length n+3 0..2 arrays with no four consecutive terms having the maximum of any two terms equal to the minimum of the remaining two terms.


1



42, 78, 146, 274, 514, 966, 1816, 3414, 6418, 12066, 22688, 42658, 80208, 150808, 283566, 533182, 1002538, 1885048, 3544452, 6664608, 12531430, 23562750, 44304934, 83306386, 156640636, 294530672, 553804746, 1041316906, 1957983912
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OFFSET

1,1


COMMENTS



LINKS



FORMULA

Empirical recurrence: a(n) = a(n1) +2*a(n2) a(n3) +3*a(n4) a(n5) 7*a(n6) +a(n7) +a(n10).
Empirical g.f.: 2*x*(21 + 18*x  8*x^2 + 7*x^3  50*x^4  71*x^5 + 15*x^6 + 4*x^7 + 7*x^8 + 12*x^9) / (1  x  2*x^2 + x^3  3*x^4 + x^5 + 7*x^6  x^7  x^10).
(End)


EXAMPLE

Some solutions for n=6
..1....1....2....2....1....0....2....1....0....0....1....0....1....0....2....1
..0....2....0....0....0....0....1....2....1....2....0....2....0....1....0....0
..0....2....1....2....1....1....2....2....2....1....2....2....2....0....0....2
..2....1....2....0....0....2....0....0....0....0....0....1....0....1....1....0
..2....0....0....1....1....2....2....1....2....2....2....0....1....0....1....2
..0....2....2....0....0....1....1....2....1....2....0....2....2....1....0....1
..1....2....1....2....2....0....2....0....0....1....1....0....0....0....0....0
..2....0....2....2....0....2....1....0....2....0....2....2....0....2....1....2
..2....1....1....0....2....2....2....2....0....2....2....0....2....2....1....0


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



