2012 AMC 10B Problems/Problem 22
Problem 22
Let (
, 
, ... 
) be a list of the first 10 positive integers such that for each 
i
either 
or 
or both appear somewhere before 
in the list. How many such lists are there?
$\textbf{(A)}\ \120\qquad\textbf{(B)}\512\qquad\textbf{(C)}\ \1024\qquad\textbf{(D)}\ 181,440\qquad\textbf{(E)}\ \362,880$ (Error compiling LaTeX. Unknown error_msg)
