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

1,1

Comments

Row 6 of A250387.

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)

Example

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

Crossrefs

Sequence in context: A175554 A263423 A266598 * A145250 A332196 A375020

Adjacent sequences: A250389 A250390 A250391 * A250393 A250394 A250395

Keyword

nonn

Author

R. H. Hardin, Nov 20 2014

Status

approved