Arjen Markus (16 april 2018) Lucky numbers are akin to prime numbers in that they are constructed via a sieve process too. They even have statistically similar properties. See this page on Mathworld for instance. The process is simple enough:

- Start with the odd numbers:

1, 3, 5, 7, 9, 11, 13, 15, 17, 19, ...

- Then, the second number in that list is 3, so remove every third number:

1, 3, 7, 9, 13, 15, 19, ...

- Then, the third number is 7, so remove every seventh number:

1, 3, 7, 9, 13, 15, ...

- And so on.

Thanks to the [lmap] command, the implementation in Tcl is also simple:

set numbers {} for {set i 1} {$i < 1000} {incr i 2} { lappend numbers $i } # # Loop over the remaining elements in the list: # Filter out the nth element each time - a simple job for [lmap] # for {set k 1} {$k < [llength $numbers]} {incr k} { set step [lindex $numbers $k] set i 0 set numbers [lmap v $numbers { incr i if {$i % $step} { set v } else { continue } }] } puts $numbers