euler012.rb

#!/usr/bin/env ruby1.9

#******************************************************************************
# The sequence of triangle numbers is generated by adding the natural
# numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 +
# 7 = 28. The first ten terms would be:
#
# 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...
#
# Let us list the factors of the first seven triangle numbers:
#  1: 1
#  3: 1,3
#  6: 1,2,3,6
# 10: 1,2,5,10
# 15: 1,3,5,15
# 21: 1,3,7,21
# 28: 1,2,4,7,14,28
#
# We can see that 28 is the first triangle number to have over five divisors.
#
# What is the value of the first triangle number to have over five
# hundred divisors?
#******************************************************************************

require "lib"

result = Triangles.new.find do |i|
  divisors_count(i) > 500
end

puts result