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

1,1

Links

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

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

Example

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

Crossrefs

Column 3 of A246737.

Sequence in context: A045205 A045295 A045280 * A214485 A045250 A258931

Adjacent sequences: A246729 A246730 A246731 * A246733 A246734 A246735

Keyword

nonn

Author

R. H. Hardin, Sep 02 2014

Status

approved