Which number does not belong in the series below?
2, 5, 10, 17, 26, 37, 50, 64
(A) 17
(B) 37
(C) 64
(D) 26
Answer: (C)
Explanation:
Given series is 2,5,10,17,26,37,50,64.
Here total number of terms are 8..i.e. A(1) to A(8).
For the 1st 7 terms, you can observe the relationship
between the terms which is
A(n) = [ A(n-1) - {A(n-1) + A(n-2)} + 2 ] where n >= 3
Now for the 8th term i.e. A(8), this relationship violates.
According to the relationship,
A(8) = [A(7) + {A(7) - A(6)} + 2 ]
= [50 + {50 - 37} + 2 ]
= 50 + 13 + 2
= 65.
But in the series it is 64. Hence 64 doesn't belong to
the series.