FactoryGirl sequences can be defined with an initial starting value

FactoryGirl.define do
  sequence :email, 1000 do |n|
    "person#{n}@example.com"
  end
end

thus:

> FactoryGirl.generate :email
=> "person1000@example.com"
> FactoryGirl.generate :email
=> "person1001@example.com"