A250392 Number of length 6+3 0..n arrays with no four consecutive terms having the maximum of any two terms equal to the minimum of the remaining two terms.

6, 966, 26578, 309452, 2160160, 10755158, 42158796, 138336744, 395723154, 1015071750, 2382851790, 5197343476, 10655843900, 20723014006, 38504379320, 68753342352, 118544772606, 198153311046, 322179959658, 510976323420

Offset: 1

Author

R. H. Hardin, Nov 20 2014

Keywords

• nonn

Comments

Row 6 of A250387.

Examples

			Some solutions for n=3:
..0....2....2....1....0....2....2....0....3....0....1....0....0....0....2....1
..2....3....0....3....1....0....0....2....0....1....0....3....1....0....0....3
..3....3....2....3....0....1....0....1....3....0....0....2....3....3....2....3
..0....2....1....2....2....3....3....3....0....2....2....0....2....2....0....2
..1....1....0....0....3....2....1....0....2....3....3....1....0....0....3....0
..3....3....0....3....1....3....2....0....1....0....3....3....3....1....3....3
..3....3....3....0....0....1....0....2....2....1....0....2....3....2....2....1
..0....0....1....3....0....3....3....1....1....0....0....3....0....0....0....3
..0....1....0....0....2....0....0....3....3....1....2....2....1....2....0....0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = n^9 - (7/30)*n^8 + (1229/315)*n^7 - (23/30)*n^6 + (49/36)*n^5 + (67/30)*n^4 - (493/180)*n^3 + (53/30)*n^2 - (11/21)*n.

Conjectures from Colin Barker, Aug 20 2017: (Start)

G.f.: 2*x*(3 + 453*x + 8594*x^2 + 43211*x^3 + 73495*x^4 + 45443*x^5 + 9692*x^6 + 549*x^7) / (1 - x)^10.

a(n) = 10*a(n-1) - 45*a(n-2) + 120*a(n-3) - 210*a(n-4) + 252*a(n-5) - 210*a(n-6) + 120*a(n-7) - 45*a(n-8) + 10*a(n-9) - a(n-10) for n>10.

(End)