Algebra Sequence — Boxes

Create a function that takes a number (step) as an argument and returns the amount of boxes in that step of the sequence.

• Step 0: Start with 0
• Step 1: Add 3
• Step 2: Subtract 1
• Repeat Step 1 & 2 ...

Examples

boxSeq(0) ➞ 0

boxSeq(1) ➞ 3

boxSeq(2) ➞ 2

Notes

• Step (the input) is always a positive integer (or zero).
• For an odd step add 3, for an even step subtract 1.