#!/usr/local/bin/perl -w

# A script for working out Aronson's sequence which is defined as
# 
# "T is the first, fourth, eleventh, sixteenth, twenty-fourth ... letter of this sentence." 
#
# The first few values are 1, 4, 11, 16, 24, 29, 33, 35, 39
#
# c.f http://www.research.att.com/cgi-bin/access.cgi/as/njas/sequences/eisA.cgi?Anum=005224

# copyright (c) Simon Wistow <simon@thegestalt.org>, 2001
# released under the terms of the GPL available from
# http://www.gnu.org/licenses/gpl.txt

# usage : takes a number which is the number of terms to calculate the sequence to

use strict;
use Lingua::EN::Numbers::Ordinate;
use Lingua::EN::Inflect qw (NUMWORDS ORD);

my @pos;
my $sentence = "T is the ";


my $limit = $ARGV[0] || 16;

while ($limit--)
{
	my $tmp;
	($tmp   = $sentence) =~ s/[^a-z]//ig; 
	my $digit  = ( defined ($pos[$#pos]) ? 
			index ($tmp, 't', $pos[$#pos]+1 ) : 
			0 
		     ) + 1;
	$sentence .= NUMWORDS ( ORD ($digit) ).", ";
	push @pos, $digit;
}

$sentence =~ s/,\s+$/ letter in this sentence./;
print "$sentence\n\n";
print join ", ", @pos;
print "\n";

exit 0;