For any natural numbers a and b that are not 0, it is stipulated that a⊗b=2*a+b, if there is: a⊗2a⊗3a⊗4a⊗5a⊗6a⊗7a⊗8a⊗9a=3039, how much is a=.
对任意不为0的自然数a，b规定a⊗b=2*a+b，若有：a⊗2a⊗3a⊗4a⊗5a⊗6a⊗7a⊗8a⊗9a=3039，求a=多少．
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