Let a book * * * have x pages (x∈Z+), then the sum of the pages of this book is (1+x)x/2.

Judging from the meaning of the question, (1+x- 1) x/2

X 2

The solution is [-1+√ (1+4× 4024)]/2

∵ [- 1+√( 1+4×4024)]/2≈62.94; √4024≈63.44; x∈Z+

∴x=63

The page number of this book is (1+x)/2 = (1+63) × 63/2 = 2016.

The wrong number is 20 16-20 12=4.