find the nth nonagonal number in ruby

A nonagonal number is a type of figurate number that represents a regular polygon with nine sides. The formula to calculate the nth nonagonal number is:

nonagonal = n * (7n - 5) / 2

To find the nth nonagonal number in Ruby, we can define a method that takes an integer n as an argument and uses the formula to calculate the nonagonal number:

main.rb
def nonagonal_number(n)
  n * (7 * n - 5) / 2
end

# Example usage
puts nonagonal_number(1) # Output: 1
puts nonagonal_number(2) # Output: 10
puts nonagonal_number(3) # Output: 27
puts nonagonal_number(4) # Output: 52
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In the above code, we have defined a method nonagonal_number that takes an integer n as an argument and calculates the nth nonagonal number using the formula. We have also provided example usage of the method to find the first 4 nonagonal numbers.