Question

nth term of sequence 1, 3, 4, 7, 12 (next number is found by adding previous 2)

Answer 1

1, 3, 4, 7, 11?

6th term = 7 + 11 = 18
7th term = 11 + 18 = 29
8th term = 18 + 29 = 47
9th term = 29  + 47 = 76
10th term = 47 + 76 = 123

Answer 2

$T_n=T_{n-1}+T_{n-2}\\\\This\ type\ of\ sequence\ is\ called\ a\ Fibonacci\ sequence.\\\\ Standard\ sequence\ is:\ 0,1,1,2,3,5,8,11,19....\\\\Tn\ has\ a\ complex\ formula\ in\ exponential\ expressions.\\\\It\ is\ not\ easy\ to\ derive\ this.$