A229006 Number of arrays of median of three adjacent elements of some length n+2 0..2 array, with no adjacent equal elements in the latter.

3, 7, 15, 31, 57, 105, 193, 353, 653, 1209, 2241, 4161, 7719, 14325, 26581, 49311, 91489, 169729, 314881, 584177, 1083761, 2010609, 3730105, 6920121, 12838307, 23817773, 44187025, 81976335, 152083481, 282147169, 523442893, 971097649

Offset: 1

Author

R. H. Hardin, Sep 10 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 2 of A229012.

Formula

Empirical: a(n) = 2*a(n-1) - a(n-3) + 2*a(n-5) - a(n-6) + 2*a(n-8) - a(n-9) + 2*a(n-11) - 2*a(n-12) + 2*a(n-13).

Empirical g.f.: x*(3 + x + x^2 + 4*x^3 + 2*x^4 + 3*x^6 + x^7 - x^8 + 2*x^9 - 2*x^11 + 2*x^12) / (1 - 2*x + x^3 - 2*x^5 + x^6 - 2*x^8 + x^9 - 2*x^11 + 2*x^12 - 2*x^13). - Colin Barker, Sep 13 2018