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EXAMPLE
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1, 2, 4, 7, 13, 24, 44, 81, 149, 274, 504, ...
1, 2, 4, 8, 16, 28, 49, 91, 169, 312, 576, ...
1, 2, 4, 8, 16, 32, 64, 112, 196, 343, 637, ...
1, 2, 4, 8, 16, 32, 64, 128, 256, 448, 784, ...
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, ...
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, ...
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, ...
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, ...
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, ...
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, ...
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For a(2,5) we count subsets of {1,...,5} that do not contain {1,3,5}, the only d=2 AP possible here. There are 4 subsets containing {1,3,5} so a(2,5) = 2^5-4 = 28.
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