The Lucas numbers are defined in the same way, but with different starting values. Let L_0 be the zeroth Lucas number and L_1 be the first. If
L_0 = 2
L_1 = 1
L_n = L_(n - 1) + L_(n - 2)
then what is the 8th Lucas number? (Note: We seek a numerical answer.)
You have defined Lucas's numbers quite well. So, why are you having problems in finding the term that you want?
L(2) ==2 + 1==3
L(3)==1 + 3 ==4
L(4)==3 + 4 ==7
L(5)==4 + 7 ==11
L(6)==7 + 11 ==18
L(7)==11 + 18==29
L(8)==18 + 29==47
Note: Your definition of Lucas's numbers, however, DOES NOT agree with other people's definition of Lucas's numbers!
For example: Wolfram/Alpha gives these as the first 10 terms:
1 | 2 | 3 | 4 | 7 | 11 | 18 | 29 | 47 | 76 (10 integers)