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Jacobsthal numbers

A positive Jacobsthal number belongs to the sequence J(0) = 0, J(1) = 1, J(n) = J(n - 1) + 2J(n - 2). Zero is excluded here.

The first few jacobsthal numbers are: 3, 5, 11, 21, 43, 85, 171, 341, 683, 1365, 2731, …

20 of the first one million positive integers are jacobsthal.

Learn more about jacobsthal numbers on wikipedia.

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