This also works.
library(shiny)
ui <- fluidPage(
tableOutput("TBL")
)
server <- function(input, output) {
output$TBL <- renderTable({
viajes <- 351419
matrix(c("a",
paste0("<strong>",formatC(viajes, digits=0, format="f"), "</strong>"," viajes"),
"c", "d"), nrow = 2)}, sanitize.text.function=function(x){x})
}
shinyApp(ui, server)