This is what might be described as a two-step sequence or two sequences spliced together.
t1 = 1
tn = - (tn-1 +1) for n = 2,4,6, ...
and tn = tn-2 + 3 for n = 3,5,7, ...
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i0 = 4; in = in-1 - 3
The rule is multiply the previous term by -1 to find the next term.
The pattern will be +2, +3, +4, +4
add 4 to every other number 1(+4)=5, 5(+4)=9 2(+4)=6
3 is the answer