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Perfect numbers: Difference between revisions
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→optimized using digital root: emphasized "known". -- ~~~~
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===optimized using digital root===
This REXX version makes use of the fact that all ''known'' perfect numbers > 6 have a ''digital root'' of '''1'''.
<lang rexx>/*REXX program tests if a number (or a range of numbers) is/are perfect.*/
parse arg low high . /*obtain the specified number(s).*/
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