Revision as of 15:23, 5 May 2009 (view source) rosettacode>Suchenwi (→‎{{header\|Smalltalk}}: + Tcl) ← Older edit		Revision as of 15:33, 23 May 2009 (view source) rosettacode>Dkf m (formatting) Newer edit →
Line 3: 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 2ⁿ2<sup>''n''</sup>-1, all ''known'' perfect numbers can derived from these primes using the formula (2<sup>''n''</sup> - 1) × 2<sup>''n'' - 1</sup>. It is not known if there are any odd perfect numbers. =={{header\|Ada}}== Line 335: =={{header\|Tcl}}== <lang tcl>proc perfect n { set sum 0 ~~proc perfect n {~~ for {set ~~sum~~i 1} {$i <= $n} {incr i} 0{ ~~for~~ ~~{set~~ i 1} if {$n % $i <== $n0} {incr sum $i} { }▼ ~~if {$n % $i == 0} {incr sum $i}~~ expr {$sum == 2$n}▼ ▲ } }</lang>▼ ▲ expr {$sum == 2$n} } ▲</lang>

Perfect numbers (view source)