RosettaCodeData/Task/Left-factorials/PowerShell/left-factorials.psh

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function left-factorial ([BigInt]$n) {
[BigInt]$k, [BigInt]$fact = ([BigInt]::Zero), ([BigInt]::One)
[BigInt]$lfact = ([BigInt]::Zero)
while($k -lt $n){
if($k -gt ([BigInt]::Zero)) {
$fact = [BigInt]::Multiply($fact, $k)
$lfact = [BigInt]::Add($lfact, $fact)
} else {
$lfact = ([BigInt]::One)
}
$k = [BigInt]::Add($k, [BigInt]::One)
}
$lfact
}
0..9 | foreach{
"!$_ = $(left-factorial $_)"
}
for($i = 10; $i -le 110; $i += 10) {
"!$i = $(left-factorial $i)"
}
for($i = 1000; $i -le 10000; $i += 1000) {
$digits = [BigInt]::Log10($(left-factorial $i))
$digits = [Math]::Floor($digits) + 1
if($digits -gt 1) {"!$i has $digits digits"}
else {"!$i has $digits digit"}
}