Semi-prime H-numbers
ID:
1179
DescriptionThis problem is based on an exercise of David Hilbert, who pedagogically
suggested that one study the theory of 4n+1 numbers.
Here, we do only a bit of that.
An H-number is a positive number which is one more than a multiple of four:
1, 5, 9, 13, 17, 21,... are the H-numbers.
For this problem we pretend that these are the only numbers.
The H-numbers are closed under multiplication.
As with regular integers, we partition the H-numbers into units,
H-primes, and H-composites.
1 is the only unit.
An H-number h is H-prime if it is not the unit,
and is the product of two H-numbers in only one way: 1 × h.
The rest of the numbers are H-composite.
For examples, the first few H-composites are: 5 × 5 = 25,
5 × 9 = 45, 5 × 13 = 65, 9 × 9 = 81, 5 × 17 = 85.
Your task is to count the number of H-semi-primes.
An H-semi-prime is an H-number which is the product of exactly two
H-primes. The two H-primes may be equal or different.
In the example above, all five numbers are H-semi-primes.
125 = 5 × 5 × 5 is not an H-semi-prime, because it's the
product of three H-primes.
InputEach line of input contains an H-number ≤ 1,000,001.
OutputFor each inputted H-number h, print a line stating h
and the number of H-semi-primes between 1 and h inclusive, separated by
one space in the format shown in the sample.
Sample Test Cases| Input | Expected Output |
|---|
1 | 1 0 |
453 | 453 33 |
721 | 721 58 |

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