Have a go yourself at working out the missing numbers in the number sequences below.
4, 8, 12, __, 20, __, __, 32, __, __, __
42, 38, 34, __, __, 22, 18, __, __, __
2, 5, 8, 11, __, __, 20, 23, __, __, __
1, 4, 9, 16, __, 36, 49, __, 81, __, 121