A246732 Number of length n+4 0..3 arrays with no pair in any consecutive five terms totalling exactly 3.

124, 260, 548, 1156, 2436, 5132, 10812, 22780, 47996, 101124, 213060, 448900, 945796, 1992716, 4198492, 8845884, 18637564, 39267844, 82734180, 174314244, 367266052, 773799948, 1630334076, 3434982396, 7237230844, 15248261636

Offset: 1

Author

R. H. Hardin, Sep 02 2014

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 3 of A246737.

Formula

Empirical: a(n) = 2*a(n-1) + a(n-4).

Empirical g.f.: 4*x*(31 + 3*x + 7*x^2 + 15*x^3) / (1 - 2*x - x^4). - Colin Barker, Nov 06 2018