Factor-perfect numbers
# 20221029 Raku programming solution
sub propdiv (\x) {
my @l = 1 if x > 1;
for (2 .. x.sqrt.floor) -> \d {
unless x % d { @l.push: d; my \y = x div d; @l.push: y if y != d }
}
@l
}
sub moreMultiples (@toSeq, @fromSeq) {
my @oneMores = gather for @fromSeq -> \j {
take @toSeq.clone.push(j) if j > @toSeq[*-1] and j %% @toSeq[*-1]
}
return () unless @oneMores.Bool;
for 0..^@oneMores {
@oneMores.append: moreMultiples @oneMores[$_], @fromSeq
}
@oneMores
}
sub erdosFactorCount (\n) {
state %cache;
my ($sum,@divs) = 0, |(propdiv n)[1..*];
for @divs -> \d {
unless %cache{my \t = n div d}:exists { %cache{t} = erdosFactorCount(t) }
$sum += %cache{t}
}
++$sum
}
my @listing = moreMultiples [1], propdiv(48);
given @listing { $_.map: *.push: 48; $_.push: [1,48] }
say @listing.elems," sequences using first definition:";
for @listing.rotor(4) -> \line { line.map: { printf "%-20s", $_ } ; say() }
my @listing2 = gather for (0..^+@listing) -> \j {
my @seq = |@listing[j];
@seq.append: 48 if @seq[*-1] != 48;
take (1..^@seq).map: { @seq[$_] div @seq[$_-1] }
}
say "\n{@listing2.elems} sequences using second definition:";
for @listing2.rotor(4) -> \line { line.map: { printf "%-20s", $_ } ; say() }
say "\nOEIS A163272:";
my ($n,@fpns) = 4, 0,1;
while (@fpns < 7) { @fpns.push($n) if erdosFactorCount($n) == $n; $n += 4 }
say ~@fpns;Output:
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