X1690: Recursion - Pell Numbers

In mathematics, the Pell Numbers follow a familiar recursive structure:

P(n) = 2 * P(n - 1) + P(n - 2) for n > 2

with initial values

Define a recursive function that gives the nth term in the Pell Number sequence.

Examples:

pellNumber(0) -> 0

pellNumber(1) -> 1

pellNumber(2) -> 2

pellNumber(3) -> 5

Your Answer:

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