[R] counting repeating sequence lengths in a vector

[Larson, TR]

Hello,
I have a very long (~50,000) sequence of repeating numbers.  The first 
100 are:

[1]     0     0     0     0     0     0     0     0     0     0     0   429
  [13]   429   429   429   429   429   429   429   858   858   858   858 
   858
  [25]   858  1287  1287  1287  1287  1287  1716  2145  2145  2574  2574 
  3003
  [37]  3003  3432  3432  3861  4290  4719  5148  5577  5577  6006  6006 
  6006
  [49]  6435  6435  6435  6864  6864  7293  7293  7293  7722  7722  7722 
  7722
  [61]  8151  8151  8151  8580  8580  8580  9009  9009  9009  9009  9438 
  9438
  [73]  9438  9438  9867  9867  9867 10296 10296 10296 10725 10725 10725 
10725
  [85] 11154 11154 11154 11154 11154 11583 11583 11583 11583 12012 12012 
12012
  [97] 12012 12441 12441 12441


What I want is to produce a vector of lengths for each contiguous run of 
numbers . i.e. for the above example, the first three items of the 
vector returned would be:

11 8 6

...to represent the counts of 0, 429, and 585, respectively.  I could do 
this with unique() and a for loop, but this would be very inefficient. 
Any advice on how to do this efficiently would be most appreciated.

thanks
Tony