how does nick recive his invite to gatsbys party

Nick actually receives an invite from Gatsby in fancy stationary while most other guests are uninvited,

I had been actually invited. A chauffeur in a uniform of robin’s-egg blue crossed my lawn early that Saturday morning with a surprisingly formal note from his employer: the honor would be entirely Gatsby’s, it said, if I would attend his “little party” that night. He had seen me several times, and had intended to call on me long before, but a peculiar combination of circumstances had prevented it — signed Jay Gatsby, in a majestic hand.