With five numbers there are 5 ways to group 4 of them together. If you take the averages of each group of 4 numbers and get...
What are the 5 numbers?
for x=1...5, leads to 1, 12, 123, 1234, 12345.
How do you define the sequence non-recursively? Can you extract the sequence directly from the averages?
flooble's webmaster puzzle