My answer is 85

1-5=4, 4*4=16

5-21=16, 16*4=64

21-85=64, 64*4=256

85-341=256, 256*4=1024

341-1365=1024

Multiply the subtracted answer with 4, we will get the answer which is the subtracted term of next two numbers. Is this logic is correct?

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What number should replace the question mark in this sequence? 1 ; 5 ; 21 ; ? ; 341 ; 1365

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