Sequences

Note that the numbers are the powers of $2$ with their digits in the reverse order. Since $821$ flipped around gives $128$ , and $2\times 128=256$ , the desired answer is $\boxed{652}$ .

This is just a simple pattern of powers of 2, but notice that the digits are reversed. Going along your powers of 2 pattern line, you get:

$1, 2, 4, 8, 16, 32, 64, 128, 256...$

Reverse the digits of all numbers now.

$1, 2, 4, 8, 61, 23, 46, 821, 652...$

Therefore, by looking at this pattern, we can see that the answer is $\boxed{652}$ . $\textbf{Ans.}$

The OEIS is a good resource for problems like these.

Flip Each number after multiplying by 2 128 * 2 = 256 after flip 652

Digits in the reverse order , multiple of 2

The numbers are powers of 2. As soon the answer reaches a double digit number, the digits reverse. So the next number is ${ 2 }^{ 8 }$ . Reverse its digits and you get 652. CHEERS!!!:)