A200882 Number of 0..4 arrays x(0..n+1) of n+2 elements without any interior element greater than both neighbors.

95, 325, 1121, 3985, 14288, 50995, 181336, 644721, 2294193, 8166441, 29066618, 103444256, 368138471, 1310164527, 4662787112, 16594519920, 59058487061, 210183969235, 748026706926, 2662163892493, 9474416502527, 33718645047381

Offset

1,1

Comments

Column 4 of A200886.

Links

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

Formula

Empirical: a(n) = 5*a(n-1) -10*a(n-2) +20*a(n-3) -15*a(n-4) +21*a(n-5) -7*a(n-6) +8*a(n-7) -a(n-8) +a(n-9).

Empirical g.f.: x*(95 - 150*x + 446*x^2 - 270*x^3 + 498*x^4 - 135*x^5 + 196*x^6 - 20*x^7 + 25*x^8) / (1 - 5*x + 10*x^2 - 20*x^3 + 15*x^4 - 21*x^5 + 7*x^6 - 8*x^7 + x^8 - x^9). - Colin Barker, Oct 16 2017

Example

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

Crossrefs

Sequence in context: A225931 A008875 A174157 * A217133 A055823 A116250

Adjacent sequences: A200879 A200880 A200881 * A200883 A200884 A200885

Keyword

nonn

Author

R. H. Hardin, Nov 23 2011

Status

approved