Create sequence of numbers, excluding certain numbers

If the numbers you want to exclude can't be generalized, @HongOoi or @James answers are the way to go. But if they can be described by some mathematical test, Filter would be more efficient.

Filter(function(x) x %% 5 != 1, 1:85)

Using setdiff:

setdiff(1:85,seq(1,85,5))
 [1]  2  3  4  5  7  8  9 10 12 ...

(1:85)[-seq(1, 85, 5)]

or is that too obvious/inefficient?