http://stackoverflow.com/q/31194315 version 2

require 'benchmark'

def get_array number, recurring
    (1..number-recurring).map {|i| [i, i]} + (number-recurring..number).map {|i| [i, i-recurring]}
end

def simons array
    hash = array.reduce({}) {|hash, pair| (hash[pair.last] ||= []).push pair.first; hash}
    hash.keys.combination(16).each do |array|
      arrays = array.map {|parent| hash[parent]}
      arrays.first.product(*arrays.drop(1)).each {|a| yield a}
    end
end

size = 0
puts Benchmark.measure do
    simons(get_array(33, 1)) do |x|
        size += 1 # or do something more interesting
    end
end
p size