"Sixty Million Trillion Combinations" is a short mystery story by American writer Isaac Asimov. It was first published in the May 5, 1980, issue of Ellery Queen's Mystery Magazine under the title "64 Million Trillion Combinations," and reprinted in Banquets of the Black Widowers (1984) and The Return of the Black Widowers (2003). Asimov originally entitled it "Fourteen Letters", but a variant of the magazine's title was used in subsequent publications of the story. The story is one of a collection of short mysteries whose characters are based loosely upon the Trap Door Spiders, a stag-club of which Asimov was a member. Source: Wikipedia (en)