A248431 - OEIS

%I #7 Nov 08 2018 08:53:21

%S 61,105,185,327,601,1105,2021,3761,6969,12815,23897,44337,81597,

%T 152209,282457,519895,969849,1799825,3312853,6180081,11468921,

%U 21110367,39381145,73083121,134521133,250947665,465706137,857206439,1599109049,2967610449

%N Number of length n+2 0..6 arrays with every three consecutive terms having the sum of some two elements equal to twice the third.

%H R. H. Hardin, <a href="/A248431/b248431.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 8*a(n-3) - 11*a(n-6) + 4*a(n-9).

%F Empirical g.f.: x*(61 + 105*x + 185*x^2 - 161*x^3 - 239*x^4 - 375*x^5 + 76*x^6 + 108*x^7 + 164*x^8) / ((1 - x)*(1 + x + x^2)*(1 - 7*x^3 + 4*x^6)). - _Colin Barker_, Nov 08 2018

%e Some solutions for n=6:

%e ..3....4....5....2....5....2....4....2....4....4....4....3....5....3....5....6

%e ..2....6....3....6....4....4....2....4....2....3....3....4....3....4....4....4

%e ..4....2....1....4....6....6....0....3....6....5....5....2....4....2....6....5

%e ..3....4....5....2....5....5....1....2....4....1....1....3....2....3....5....3

%e ..5....3....3....3....4....4....2....4....2....3....3....4....6....1....4....1

%e ..1....2....4....4....3....3....3....6....0....2....2....2....4....2....3....2

%e ..3....4....2....5....5....2....4....2....4....1....4....3....5....3....2....3

%e ..5....0....6....3....4....4....5....4....2....0....0....1....3....4....4....4

%Y Column 6 of A248433

%K nonn

%O 1,1

%A _R. H. Hardin_, Oct 06 2014