A209604 - OEIS

%I #5 Mar 31 2012 12:37:29

%S 1,2,11,45,170,538,1674,5410,18001,60486,202486,674159,2238695,

%T 7433743,24704751,82150290,273210105,908536081,3020918528,10044214676,

%U 33396046046,111040661940,369210326847,1227626858414,4081857794878

%N Number of nX2 1..2 arrays with every element value z a city block distance of exactly z from another element value z

%C Column 2 of A209610

%H R. H. Hardin, <a href="/A209604/b209604.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 3*a(n-1) +5*a(n-4) +16*a(n-5) +23*a(n-6) +6*a(n-7) -6*a(n-8) -21*a(n-9) -8*a(n-10) -9*a(n-11) -5*a(n-12) -4*a(n-13) +a(n-15) for n>16

%e Some solutions for n=4

%e ..2..2....2..2....2..2....1..2....2..2....1..1....1..1....1..2....2..1....1..2

%e ..2..1....2..2....1..2....1..2....2..1....1..1....1..2....1..2....2..1....1..2

%e ..2..1....2..2....1..2....1..2....2..1....2..2....2..1....2..2....2..2....1..2

%e ..1..1....2..2....2..2....1..2....2..2....2..2....1..1....2..2....1..1....2..2

%K nonn

%O 1,2

%A _R. H. Hardin_ Mar 10 2012