A250375 Number of length 2+6 0..n arrays with every seven consecutive terms having the maximum of some three terms equal to the minimum of the remaining four terms.

151, 3096, 24566, 119235, 428421, 1256106, 3179756, 7202421, 14952595, 28938316, 52861986, 92002391, 153670401, 247744830, 387294936, 589296041, 875444751, 1273080256, 1816218190, 2546703531, 3515489021, 4784045586, 6425911236

Offset

1,1

Links

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

Formula

Empirical: a(n) = (9/7)*n^7 + (37/3)*n^6 + (65/2)*n^5 + 46*n^4 + (217/6)*n^3 + (97/6)*n^2 + (233/42)*n + 1.

Conjectures from Colin Barker, Nov 13 2018: (Start)

G.f.: x*(151 + 1888*x + 4026*x^2 + 939*x^3 - 417*x^4 - 114*x^5 + 8*x^6 - x^7) / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>8.

(End)

Example

Some solutions for n=4:
..3....1....2....2....2....0....4....2....3....3....0....1....2....2....3....3
..1....1....3....1....2....2....0....3....3....4....3....1....1....4....1....0
..4....2....1....1....2....1....2....0....3....3....3....3....1....0....4....1
..1....1....4....0....1....1....3....4....3....3....2....1....1....2....1....0
..0....0....0....3....1....3....1....2....4....3....2....3....0....4....1....3
..4....2....1....1....3....1....2....2....3....3....3....1....3....4....0....1
..0....1....1....1....2....0....4....4....2....4....2....1....3....0....1....4
..2....0....0....2....4....2....3....1....2....2....1....1....1....2....2....1

Crossrefs

Row 2 of A250373

Sequence in context: A340436 A211555 A143012 * A060889 A206362 A200934

Adjacent sequences: A250372 A250373 A250374 * A250376 A250377 A250378

Keyword

nonn

Author

R. H. Hardin, Nov 19 2014

Status

approved