The writer Arthur has n≥1 co-authors who write books with him. Each book has a list of authors including Arthur himself. No two books have the same set of authors. At a party with all his co-author, each co-author writes on a note how many books they remember having written with Arthur. Inspecting the numbers on the notes, they discover that the numbers written down are the first n Fibonacci numbers (defined by F1=F2=1 and Fk+2=Fk+1+Fk). For which n is it possible that none of the co-authors had a lapse of memory? combinatoricsFibonacciFibonacci NumbersFibonacci sequence