Number Tracks

They are all odd numbers.

They go up in 4s because each number on each strip is 2 more than the one on the previous strip and there are two numbers 2 x 2 = 4

All the 3 bits are divisible by 3 and the 5 bits divisible by 5.

The sums increase by 3 x 3 and 5 x 5 on each strip because each number on each strip is 3 (5) more than the corresponding one on the previous strip.

With strips of length 4n + 1 and 4n + 3 the sums are always in the multiplication tables.

If the length of the strip is of the order 4n + 2 you always get an odd total.

If the length of the strip is 4n you always get an even total and the totals are not in the corresponding multiplication tables.