. ▁The ▁book ▁also ▁includes ▁discuss ions ▁on ▁the ▁nature ▁of ▁mathematics ▁and ▁the ▁use ▁of ▁computers ▁in ▁mathematics . ▁ ▁After ▁an ▁intro duct ory ▁chapter ▁on ▁Sud oku ▁and ▁its ▁ded uct ive ▁puzz le - sol ving ▁techniques ▁( also ▁touch ing ▁on ▁E uler ▁t ours ▁and ▁Hamiltonian ▁cycles ), ▁the ▁book ▁has ▁eight ▁more ▁chap ters ▁and ▁an ▁ep ilog ue . ▁Chap ters ▁two ▁and ▁three ▁discuss ▁Latin ▁squares , ▁the ▁thirty - six ▁officers ▁problem , ▁Leon hard ▁E uler ' s ▁incorrect ▁conject ure ▁on ▁Gra ec o - Lat in ▁squares , ▁and ▁related ▁topics . ▁Here , ▁a ▁Latin ▁square ▁is ▁a ▁grid ▁of ▁numbers ▁with ▁the ▁same ▁property ▁as ▁a ▁Sud oku ▁puzz le ' s ▁solution ▁of ▁having ▁each ▁number ▁appear ▁once ▁in ▁each ▁row ▁and ▁once ▁in ▁each ▁column . ▁They ▁can ▁be ▁trac ed ▁back ▁to ▁mathematics ▁in ▁medieval ▁Islam , ▁were ▁studied ▁recre ation ally ▁by ▁Benjamin ▁Franklin , ▁and ▁have ▁seen ▁more ▁serious ▁application ▁in ▁the ▁design ▁of ▁experiments ▁and ▁in ▁error ▁correction ▁codes . ▁Sud oku ▁puzz les ▁also ▁const rain ▁square ▁blocks ▁of ▁cells ▁to ▁contain ▁each ▁number ▁once , ▁making ▁a ▁restricted ▁type ▁of ▁Latin ▁square ▁called ▁a ▁g ere chte ▁design . ▁ ▁Chap ters ▁four ▁and ▁five ▁concern ▁the ▁combin atorial ▁enumer ation ▁of ▁completed ▁Sud oku ▁puzz les , ▁before ▁and ▁after ▁factor ing ▁out ▁the ▁symmet ries ▁and ▁equivalence ▁classes ▁of ▁these ▁puzz les ▁using ▁Burn side ' s ▁lemma