#!/bin/env perl

use Modern::Perl;

say "A(0,$_) ", A(0, $_) for 0..9;
say "A(1,$_) ", A(1, $_) for 0..9;
say "A(2,$_) ", A(2, $_) for 0..9;
say "A(3,$_) ", A(3, $_) for 0..9;

my @pool;

sub A {
    my ($m, $n) = @_;
    die "parameter less than 0\n" if $m < 0 or $n < 0;

    return $pool[$m][$n] if defined $pool[$m][$n];

    if ($m == 0) {
        $pool[0][$n] = $n + 1;
    } elsif ($n == 0) {
        $pool[$m][0] = A($m - 1, 1);
    } else {
        $pool[$m][$n] = A($m - 1, A($m, $n - 1));
    }

    return $pool[$m][$n];
}