A200883 Number of 0..5 arrays x(0..n+1) of n+2 elements without any interior element greater than both neighbors.
161, 636, 2507, 10213, 42182, 173606, 710976, 2908797, 11911516, 48807427, 199987737, 819315100, 3356387171, 13749952752, 56330082115, 230771042950, 945410224602, 3873094298871, 15867039092263, 65003096433432
Offset: 1
Keywords
Examples
Some solutions for n=3 ..4....3....5....4....3....5....2....2....1....2....4....0....1....2....2....4 ..4....4....2....0....5....3....1....4....2....2....1....2....0....4....0....0 ..3....4....1....0....5....1....2....4....4....4....1....3....0....4....1....3 ..1....0....0....2....5....1....2....1....4....4....1....3....1....4....3....3 ..0....2....1....5....3....0....3....4....4....0....2....0....3....1....3....3
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Formula
Empirical: a(n) = 6*a(n-1) -15*a(n-2) +35*a(n-3) -35*a(n-4) +56*a(n-5) -28*a(n-6) +36*a(n-7) -9*a(n-8) +10*a(n-9) -a(n-10) +a(n-11).
Empirical g.f.: x*(161 - 330*x + 1106*x^2 - 924*x^3 + 1884*x^4 - 792*x^5 + 1252*x^6 - 264*x^7 + 355*x^8 - 30*x^9 + 36*x^10) / (1 - 6*x + 15*x^2 - 35*x^3 + 35*x^4 - 56*x^5 + 28*x^6 - 36*x^7 + 9*x^8 - 10*x^9 + x^10 - x^11). - Colin Barker, Oct 16 2017
Comments