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Number of (n+2)X(2+2) 0..1 arrays with each row and column divisible by 7, read as a binary number with top and left being the most significant bits.
2

%I #5 Sep 17 2015 22:20:03

%S 3,5,9,27,61,145,435,1253,3593,10779,32445,96881,290643,875365,

%T 2627721,7883163,23685949,71096657,213289971,640160485,1920877321,

%U 5762631963,17289819325,51872540977,155617622931,466863471461,1400610395529

%N Number of (n+2)X(2+2) 0..1 arrays with each row and column divisible by 7, read as a binary number with top and left being the most significant bits.

%C Column 2 of A262319.

%H R. H. Hardin, <a href="/A262314/b262314.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 4*a(n-1) -4*a(n-2) +20*a(n-3) -68*a(n-4) +68*a(n-5) -162*a(n-6) +444*a(n-7) -444*a(n-8) +644*a(n-9) -1244*a(n-10) +1244*a(n-11) -1277*a(n-12) +1376*a(n-13) -1376*a(n-14) +1032*a(n-15)

%e Some solutions for n=4

%e ..0..1..1..1....0..1..1..1....1..1..1..0....1..1..1..0....0..1..1..1

%e ..0..1..1..1....0..1..1..1....1..1..1..0....0..0..0..0....1..1..1..0

%e ..1..1..1..0....0..1..1..1....1..1..1..0....0..0..0..0....0..1..1..1

%e ..1..1..1..0....1..1..1..0....1..1..1..0....0..0..0..0....1..1..1..0

%e ..1..1..1..0....1..1..1..0....1..1..1..0....1..1..1..0....0..1..1..1

%e ..0..1..1..1....1..1..1..0....1..1..1..0....1..1..1..0....1..1..1..0

%Y Cf. A262319.

%K nonn

%O 1,1

%A _R. H. Hardin_, Sep 17 2015