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#!/usr/bin/env perl
#
# Write a script to generate Van Eck’s sequence starts with 0
# (https://en.wikipedia.org/wiki/Van_Eck%27s_sequence)
################################################################################
use strict;
use warnings;
my $iterations = shift or die "Usage: $0 <iterations>\n";
# Computed sequence
my @vaneck = (0);
# Map numbers to the last time they appear in sequence
my %lastpos = (0 => 0);
# For every n, compute (push) n+1
foreach my $n (0 .. $iterations-2) {
my $curn = $vaneck[$n];
my $m = $lastpos{$curn};
my $nextn = defined $m ? $n-$m : 0;
push @vaneck, $nextn;
$lastpos{$curn} = $n;
}
print "@vaneck\n";
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