In R: How can I check that I have consecutive years of data (to later be able to calculate growth)?

I have the dataframe (sample) below:

companyID   year   yearID
    1       2010     1
    1       2011     2
    1       2012     3
    1       2013     4
    2       2010     1
    2       2011     2
    2       2016     3
    2       2017     4
    2       2018     5
    3       2010     1
    3       2011     2
    3       2014     3
    3       2017     4
    3       2018     5

I have used a for loop in order to try and create a sequence column that starts a new number for each new sequence of numbers. I am new to R so my definitions may be a bit wrong. My for loop looks like this:

size1 <- c(1:3)
s <- 0
for (val1 in size) {
  m <- max(sample[sample$companyID == val1, 4])
  size2 <- c(1:m)
  for (val2 in size2){ 
    row <- sample[which(sample$companyID == val1 & sample$yearID == val2)]
    m1 <- sample[sample$companyID == val1 & sample$yearID == val2, 2]
    m2 <- sample[sample$CompanyID == val1 & sample$yearID == (val2-1), 2]
    if(val2>1 && m1-m2 > 1) {
                  sample$sequence[row] s = s+1}
    else {s = s}
  }
  }

Where m is the max value of the yearID per companyID, row is to identify that the value should be entered on the row where companyID = val1 and yearID = val2, m1 is from the year variable and is the latter year, whereas m2 is the former year. What I have tried to do is to change the sequence every time m1-m2 > 1 (when val2 > 1 also).

Desired outcome:

companyID   year   yearID   sequence
    1       2010     1          1
    1       2011     2          1
    1       2012     3          1
    1       2013     4          1
    2       2010     1          2
    2       2011     2          2
    2       2016     3          3
    2       2017     4          3
    2       2018     5          3
    3       2010     1          4
    3       2011     2          4
    3       2014     3          5
    3       2017     4          6
    3       2018     5          6

Super appreciative if anyone can help!!