Just a thought...

two digits squared is easy.  ie. 58

5 squared (25) together with 8 squared (64) is 2564 (remember)

take the 50 and multiply it by 8 to get 400.  Double your answer everytime, in this case it's 400 twice = 800.

2564 + 800 = 3364

58 squared = 3364

With a bit of practice you can do it yourself while you're on my way home in your/my head.