Question

A series consists of some numbers such that the summation of the divisors of any number of that series is 1 less than twice of that number. For example, the divisors of 4 are 1,2 and 4 and the sum is 7. If the numbers of this sequence are arranged in ascending order then what is the 9th term?

Answer 1

The 9th term of the series is 256

Explanation:

Here we have the numbers as follows

1, 2, 4 from we have;

1 = The first term of the series

2 = The second term of the series

4 = The third term of the series

From the definition of the series, the sum of the factors is 1 less than twice the number, therefore, since 4 satisfies all the conditions, we observe that;

4×2×1 = 8 also satisfies all the conditions, hence we have;

8 = The fourth term of the series

8 × 2 = 16 = The fifth term of the series

16 × 2 = 32 = The sixth term of the series

32 × 2 = 64 = The seventh term of the series

64 × 2 = 128 = The eight term of the series

Therefore, the 9th term of the series = 128 × 2 = 256.