use utf8; use strict; use warnings; use feature 'say'; use List::Util 'uniq'; sub prime_factors { my ($n, $d, @factors) = (shift, 1); while ($n > 1 and $d++) { $n /= $d, push @factors, $d until $n % $d; } @factors } sub μ { my @p = prime_factors(shift); @p == uniq(@p) ? 0 == @p%2 ? 1 : -1 : 0; } my @möebius; push @möebius, μ($_) for 1 .. (my $upto = 199); say "Möbius sequence - First $upto terms:\n" . (' 'x4 . sprintf "@{['%4d' x $upto]}", @möebius) =~ s/((.){80})/$1\n/gr;