#!/usr/bin/ruby
 
class An
 
    def initialize(k = 1, t = 10)
        @k   = k
        @t   = t
        @mem = Hash.new
    end
 
    def a(k, n)
 
        # Recall from memory.
        key = "#{k},#{n}"
        return @mem[key] unless @mem[key] == nil
 
        # Otherwise compute and remember.
        return (@mem[key] = 1) if (k == 0) and (n == 0)
        return (@mem[key] = 0) if (k  < 0)  or (n  < 0) 
        @mem[key] = a(k-1, n) + a(k-1, n-1) + a(k-1, n-2) + a(k-1, n-3)
    end
 
    def terms
         (0 .. @t).map { |n| a(@k, n) }
    end
 
    def print
        puts terms().join(',') 
    end
end
 
# Print the initial ten terms of the first few sequences.
(0 .. 15).each do |k|
    print "k = #{k}: "
    An.new(k, 10).print
end

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