Misc of Ruby

algo.rb

#!/usr/bin/env ruby

print "input n: "
n = gets.chomp.to_i

r = 0
(1..(n - 1)).each do |i|
	((i + 1)..(n)).each do |j|
    (1..j).each {r += 1}
  end
end
puts "The algo4: #{r}"

m = n * (n + 1) * (n - 1) / 3
puts "The formula: #{m}"

r = 0
(1..n).each do |i|
  (1..i).each do |j|
    (j..(i+j)).each {r += 1}
  end
end
puts "The algo5: #{r}"

m = n * (n + 1) * (n + 2) / 3
puts "The formula: #{m}"

r = 0
(1..n).each do |i|
  (1..i).each do |j|
    (j..i+j).each do |k|
      (1..i+j-k).each { r += 1 }
    end
  end
end
puts "The algo6: #{r}"

m = n * (n + 1) * (3 * n + 1) * (n + 2) / 24
puts "The formula: #{m}"

r = 0
k = 0
(1..n).each do |i|
  (i+1..n).each  do |j|
    ((i+j-1)..n).each {r += 1}
  end
end
puts "The algo7: #{r}"

if n % 2 == 0
  m = n * (n + 2) * (2 * n - 1) / 24
else
  m = (n - 1) * (n + 1) * (2 * n + 3) / 24
end
puts "The formula: #{m}"