A247720 Number of length n+3 0..2 arrays with no disjoint pairs in any consecutive four terms having the same sum

48, 90, 172, 334, 656, 1300, 2584, 5148, 10272, 20520, 41008, 81976, 163904, 327760, 655456, 1310832, 2621568, 5243040, 10485952, 20971744, 41943296, 83886400, 167772544, 335544768, 671089152, 1342177920, 2684355328, 5368710016

Offset

1,1

Comments

Column 2 of A247726

Links

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

Formula

Empirical: a(n) = 2*a(n-1) +2*a(n-4) -4*a(n-5).

Empirical G.f.: -2*x*(-24+3*x+4*x^2+5*x^3+54*x^4) / ( (2*x-1)*(2*x^4-1) ). - R. J. Mathar, Sep 23 2014

Example

Some solutions for n=6
..1....2....2....2....2....2....1....0....2....2....1....0....1....0....1....2
..0....1....0....0....0....0....0....0....0....2....2....2....2....2....0....2
..0....0....1....2....2....0....0....2....1....2....0....2....0....2....2....1
..0....0....2....1....1....1....2....0....2....0....0....1....2....1....0....2
..1....0....0....0....2....0....1....1....0....2....1....2....2....2....0....2
..0....1....0....2....2....2....2....0....0....2....2....2....2....0....0....0
..0....2....0....0....2....2....0....2....1....1....0....0....1....0....1....1
..2....0....1....1....0....1....2....0....0....0....2....1....2....1....0....2
..1....2....0....0....1....2....2....0....0....2....2....2....2....2....2....0

Crossrefs

Sequence in context: A260106 A260099 A224546 * A204647 A260980 A260070

Adjacent sequences: A247717 A247718 A247719 * A247721 A247722 A247723

Keyword

nonn

Author

R. H. Hardin, Sep 23 2014

Status

approved