数学白痴竟然也难以置信的事

1，2，6， 42， 1806， ____?

几天前，检查邮件时发现了朋友转寄过来动一动脑筋的数学题，于是，打开来看。

If you're an engineer, you should be able to solve it in (under) three minutes (more like 30 seconds), if you're an architect, in three hours; if you're a doctor, in six hours; if you're an accountant, in three months and if you're a lawyer, probably never. 
if you're good at math or logical problems, solve this challenge and the answer is the password to open the spreadsheet to which you can add your name to the hall of fame. 
What is the missing number in this logical series? 

像偶这个数学白痴，竟然可以在短短的时间内似乎找到答案了。兴奋之际却又不晓得答对还是答错了？

答错的话，应该的嘛！哪有那么简单的解答？

答对的话，却不可能这么聪明/侥幸，这么轻而易举地找到解答？

真是对也担心，错也担心！

经由一位朋友的证实后，偶只好承认自己有那么地一丁点小聪明了咯，哇哈哈哈哈！=D