Generate vector of a repeated string with incremental suffix number

An alternative to paste is sprintf, which can be a bit more convenient if, for instance, you wanted to "pad" your digits with leading zeroes.

Here's an example:

sprintf("Fst%d", 1:10)     ## No padding
# [1] "Fst1"  "Fst2"  "Fst3"  "Fst4"  "Fst5"  
# [6] "Fst6"  "Fst7"  "Fst8"  "Fst9"  "Fst10"
sprintf("Fst%02d", 1:10)   ## Pads anything less than two digits with zero
# [1] "Fst01" "Fst02" "Fst03" "Fst04" "Fst05" 
# [6] "Fst06" "Fst07" "Fst08" "Fst09" "Fst10"

So, for your question, you would be looking at:

sprintf("Fst%d", 1:100) ## or sprintf("Fst%03d", 1:100)

You can use the paste function to create a vector that combines a set character string with incremented numbers: paste0('Fst', 1:100)