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− | In mathematics, the '''Sieve of Eratosthenes''' (Greek: κόσκινον Ἐρατοσθένους) is |
+ | In mathematics, the '''Sieve of Eratosthenes''' (Greek: κόσκινον Ἐρατοσθένους) is a way to obtain a list of all the prime numbers up until a given point. |
− | The |
+ | The method works by methodically crossing out the composite numbers. The user will cross out the multiples of each prime, from 2 and up until the square root of the final number. The numbers that are not crossed off are prime numbers. |
− | + | The algorithm is named after Eratosthenes of Cyrene, a Greek mathematician. |
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+ | |||
+ | ==How to Use the Sieve== |
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⚫ | |||
+ | #List all the numbers from 1 to a certain number. |
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+ | #Cross out 1, since it is neither prime nor composite. |
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+ | #Circle 2 and cross out every other multiple of 2. |
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⚫ | |||
+ | #Circle 5 and cross out every other multiple of 5. |
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+ | #Circle 7 and cross out every other multiple of 7. |
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+ | #Circle the lowest number remaining after the previous step and cross out all its multiples. |
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+ | #Repeat Step 7 until every number has either been crossed out or circled. |
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− | ==Example of how to do the sieve== |
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⚫ | |||
− | #Cross out 1. It is a special number. |
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− | #Encircle 2. Cross out all multiples of 2. |
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⚫ | |||
− | #Encircle 5. Cross out all multiples of 5. |
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− | #Encircle 7. Cross out all multiples of 7. |
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− | #Encircle all the rest of the numbers. They're prime. |
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==References== |
==References== |
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#https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes |
#https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes |
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+ | {{Important Pages}} |
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[[Category:Important Pages]] |
[[Category:Important Pages]] |
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+ | [[Category:History of Prime Numbers]] |
Latest revision as of 11:36, 27 January 2018
In mathematics, the Sieve of Eratosthenes (Greek: κόσκινον Ἐρατοσθένους) is a way to obtain a list of all the prime numbers up until a given point.
The method works by methodically crossing out the composite numbers. The user will cross out the multiples of each prime, from 2 and up until the square root of the final number. The numbers that are not crossed off are prime numbers.
The algorithm is named after Eratosthenes of Cyrene, a Greek mathematician.
How to Use the Sieve
- List all the numbers from 1 to a certain number.
- Cross out 1, since it is neither prime nor composite.
- Circle 2 and cross out every other multiple of 2.
- Circle 3 and cross out every other multiple of 3.
Tip: Just add 6 to the first number, because all even numbers are crossed out. - Circle 5 and cross out every other multiple of 5.
- Circle 7 and cross out every other multiple of 7.
- Circle the lowest number remaining after the previous step and cross out all its multiples.
- Repeat Step 7 until every number has either been crossed out or circled.