What is the missing number in the sequence 28 36?

Answer 1

Any number at all can be fitted as the missing number in a such a sequence.

The simplest is 32 with the rule: Un = 4*n + 24

Next there is 31.749 with the rule Un = 24.694*1.134n

But, given any number, it is easy to find a rule which will work - even though it may look a pretty clumsy rule.

Suppose you want some number x to be the missing number. Then consider

a = 32 - x

b = -124 + 4x

c = 120 - 3x

then Un = an2 + bn + c will do the trick.