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July 11th, 2009, 02:56 AM   #1
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Serial position of a composite number

I need a software/web based utility that would provide the serial position of a composite number among the composite numbers. For example, providing it with 27 it would return 17.
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July 11th, 2009, 04:57 AM   #2
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Re: Serial position of a composite number

1. Download Pari/gp (link in my sig; use the windows installer if you're on windows!)
2. Type or paste in the following program:
Code:
position(n)=n-primepi(n)-1
3. Find the position of any composite by typing, e.g., position(27).
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