In simple words sequence is a list of numbers written in definite order: a1,a2,…,an{a}_{{1}},{a}_{{2}},\ldots,{a}_{{n}}a1,a2,…,an. a1{a}_{{1}}a1 is first term, a2{a}_{{2}}a2 is second term, and, in general, an{a}_{{n}}an is n-th term. We deal with infinite sequences, so each term an{a}_{{n}}an will have a successor an+1{a}_{{{n}+{1}}}an+1.
