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mirror_sequence

Language/Type: PHP recursion

Write a recursive function named mirror_sequence that accepts an integer parameter $n and prints a sequence of $n integers, descending from $n to 1 and then ascending back from 1 to $n as in the table below.

Call Output
mirror_sequence(1); 1
mirror_sequence(2); 1 1
mirror_sequence(3); 2 1 2
mirror_sequence(4); 2 1 1 2
mirror_sequence(5); 3 2 1 2 3
mirror_sequence(6); 3 2 1 1 2 3
mirror_sequence(7); 4 3 2 1 2 3 4
mirror_sequence(8); 4 3 2 1 1 2 3 4
mirror_sequence(9); 5 4 3 2 1 2 3 4 5
mirror_sequence(10); 5 4 3 2 1 1 2 3 4 5

Note that for odd numbers the sequence has a single 1 in the middle, while for even values it has two 1s in the middle. Your function should throw an Exception if passed a value less than 1.

Function: Write a PHP function as described, not a complete program.

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