Find Missing terms in interpolation table

x	f(x)
1	2
2	4
3	8
4	?
5	32
6	64
7	128

Solution:
The value of table for `x` and `y`

x	1	2	3	4	5	6	7
y	2	4	8	?	32	64	128

Here we are given 6 values of y. We assume that y is polynomial of degree 5.
Hence `Delta^6 y_0=0`

`(E-1)^6 y_0=0`

`(E^6-6E^5+15E^4-20E^3+15E^2-6E+1) y_0=0`

`y_6-6y_5+15y_4-20y_3+15y_2-6y_1+y_0=0`

`:.128-6(64)+15(32)-20(a)+15(8)-6(4)+2=0`

`:.-20a+322=0`

`:.-20a=-322`

`:.a=(-322)/(-20)`

`:.a=16.1`

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