sequence that counts up and back down

I hit a minor sticking point working one of the problems in 'Using R' 
(Verzani).  I'm having difficulty with generating a sequence that goes 
1, 2, 3, 4, 5, 4, 3, 2, 1.  I can make one that counts up, I can make 
one that counts down, etc. but one that counts up then down like this 
(short of just using c() ) is stumping me.

Any help (on or off list) would be appreciated.

Thanks,

Monte