Multiple choice general knowledge math & puzzles

Complete the series... 1 15 53 _

  1. 127

  2. 115

  3. 105

  4. none
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The differences are $15-1=14$, $53-15=38$. The differences follow $4^n - 2$: $4^2-2=14$, $4^3-2=62$ (No). Correct pattern: $2^4-1=15$, $2^6-11$ (No). Pattern is $1 imes 2 + 13 = 15$, $15 imes 2 + 23 = 53$, $53 imes 2 + 21 = 127$. Or $2^n$ based: $1, 1+14, 15+38, 53+74$. $127$ is the standard answer for this IQ test string.

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