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Perfect numbers: Difference between revisions
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→[[Perfect Numbers#ALGOL 68]]: (2ⁿ-1) × 2ⁿ ÷ 2
m (→[[Perfect Numbers#ALGOL 68]]: c.f. Lucas-Lehmer_test for even perfect numbers of the form: (2ⁿ-1) × 2ⁿ/2) |
m (→[[Perfect Numbers#ALGOL 68]]: (2ⁿ-1) × 2ⁿ ÷ 2) |
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A number is perfect if the sum of its factors is equal to twice the number. An equivalent condition is that <tt>n</tt> is perfect if the sum of <tt>n</tt>'s factors that are less than <tt>n</tt> is equal to <tt>n</tt>.
Note: The faster [[Lucas-Lehmer_test]] is used to find primes of the form 2ⁿ-1, all ''known'' perfect numbers can derived from these primes using the formular <tt>(2ⁿ-1) × 2ⁿ
=={{header|Ada}}==
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