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 = 1
L_1 = 3
L_n = L_(n - 1) + L_(n - 2)
Find L_(20)
By your count, here are first 20 Lucas numbers.
1 , 3 , 4 , 7 , 11 , 18 , 29 , 47 , 76 , 123 , 199 , 322 , 521 , 843 , 1364 , 2207 , 3571 , 5778 , 9349 , 15127, 24476 [This is the 20th Lucas number by your count!!].
