r/askmath • u/Novel_Arugula6548 • 3d ago
Analysis Does anyone know a simple proof to show that a_1 + 2a_2 + 4a_4 +8a_8 + ... is bounded when the a_n's are all positive and decreasing?
I'm not sure how to find or compare the rate of growth of 2n with any positive decreasing sequence, in order to find the exact cutoff point where some positive decreasing sequence decreases slower than 2n increases.
How do I find that exact cutoff point in this situation?
The series in the title only converges when the all positive decreasing sequence (a_n) decreases faster than 2n increases.




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Were they stupid?
in
r/mathmemes
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17h ago
Wouldn't the new design just get shot at differently?