Answer
$a_{2}$=4
$a_{3}$=11
$a_{4}$=26
Work Step by Step
$a_{2}$=2$a_{2-1}$+2 = 2.$a_{1}$+2 = 2.1+2 = 4
$a_{3}$=2$a_{3-1}$+3 = 2.$a_{2}$+3 = 2.4+3 = 11
$a_{4}$ =2$a_{4-1}$ +4 = 2.$a_{3}$+4 = 2.11+4 =26
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