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A184048
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T(n,k) = 1/9 the number of (n+1) X (k+1) 0..2 arrays with all 2 X 2 subblocks having the same four values.
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11
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9, 15, 15, 25, 21, 25, 45, 31, 31, 45, 81, 51, 41, 51, 81, 153, 87, 61, 61, 87, 153, 289, 159, 97, 81, 97, 159, 289, 561, 295, 169, 117, 117, 169, 295, 561, 1089, 567, 305, 189, 153, 189, 305, 567, 1089, 2145, 1095, 577, 325, 225, 225, 325, 577, 1095, 2145, 4225, 2151
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OFFSET
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1,1
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COMMENTS
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Table starts
....9...15...25...45...81..153..289..561.1089.2145.4225..8385.16641.33153.66049
...15...21...31...51...87..159..295..567.1095.2151.4231..8391.16647.33159.66055
...25...31...41...61...97..169..305..577.1105.2161.4241..8401.16657.33169.66065
...45...51...61...81..117..189..325..597.1125.2181.4261..8421.16677.33189.66085
...81...87...97..117..153..225..361..633.1161.2217.4297..8457.16713.33225.66121
..153..159..169..189..225..297..433..705.1233.2289.4369..8529.16785.33297.66193
..289..295..305..325..361..433..569..841.1369.2425.4505..8665.16921.33433.66329
..561..567..577..597..633..705..841.1113.1641.2697.4777..8937.17193.33705.66601
.1089.1095.1105.1125.1161.1233.1369.1641.2169.3225.5305..9465.17721.34233.67129
.2145.2151.2161.2181.2217.2289.2425.2697.3225.4281.6361.10521.18777.35289.68185
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LINKS
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FORMULA
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Empirical, for all rows and columns: a(n)=3*a(n-1)-6*a(n-3)+4*a(n-4).
The above empirical formula is correct.
T(n,k) = -7 + 4*(2^(n-1) + 2^(k-1)) + 2*(2^(floor((n-1)/2)) + 2^(floor(n/2)) + 2^(floor((k-1)/2)) + 2^(floor(k/2))). (End)
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EXAMPLE
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Some solutions for 6X5
..0..1..0..1..0....1..2..1..2..1....1..2..1..2..1....2..1..2..2..2
..0..1..0..1..0....1..2..1..2..1....1..0..1..0..1....0..2..0..1..0
..1..0..1..0..1....2..1..2..1..2....1..2..1..2..1....2..1..2..2..2
..0..1..0..1..0....1..2..1..2..1....1..0..1..0..1....0..2..0..1..0
..0..1..0..1..0....1..2..1..2..1....2..1..2..1..2....2..1..2..2..2
..1..0..1..0..1....2..1..2..1..2....0..1..0..1..0....0..2..0..1..0
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PROG
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(PARI) T(n, k) = my(m=3, b=t->2^t-1); m^2 + (m-1)^2*(b(n-1) + b(k-1)) + (m-1)*(b((n-1)\2) + b(n\2) + b((k-1)\2) + b(k\2)) \\ Andrew Howroyd, Mar 09 2024
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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