Question 1209828
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The sequence with first two terms 2 and 1 with the recursive definition that each term is the sum of the previous two terms is NOT "THE" Lucas sequence.  A Lucas sequence is ANY sequence in which each term is a linear combination of the two preceding terms (and the first two terms can be any numbers).<br>
The sequence in this problem is A Lucas sequence with first two terms 2 and 1.<br>
Subsequent terms of the sequence are found using the given recursive definition.<br>
L(0)=2
L(1)=1
L(2)=L(0)+L(1)=2+1=3
L(3)=L(1)+L(2)=1+3=4
L(4)=L(2)+L(3)=3+4=7
L(5)=L(3)+L(4)+4+7=11
etc...<br>
ANSWER: L(4)=7<br>