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

1,1

Links

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

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

Example

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

Crossrefs

Column 2 of A229012.

Sequence in context: A222813 A304078 A151338 * A023424 A276647 A006778

Adjacent sequences: A229003 A229004 A229005 * A229007 A229008 A229009

Keyword

nonn

Author

R. H. Hardin, Sep 10 2013

Status

approved