2014 AIME II Problems/Problem 15

Solution

Note that (in base 2 for the indices, base 10 for the values) $a_1$ = 2, $a_{10}$ = 3, $a_{11}$ = 2 * 3 = 6, ..., $a_{10010101}$ = 2 * 5 * 11 * 19 = 2090. Thus, t = 10010101 (base 2) = $\boxed{149}$ .

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2014 AIME II Problems/Problem 15

Solution