library(ggplot2)

LEVELS = 4

mylabels = c(
  expression(paste(3^4,"= 81")),
  expression(paste(3^3,"= 27")),
  expression(paste(3^2,"= 9")),
  expression(paste(3^1,"= 3")),
  expression(paste(3^0,"= 1")))
mylabels
length(mylabels)


df=data.frame(x=runif(40),y=(runif(40)*10)%%5)
p = ggplot(df,aes(x,y))  +
  geom_point() +
  scale_y_continuous(breaks = 0:LEVELS, labels = mylabels)
p

mylabels=c(paste("expression(paste(3^",LEVELS:0,'," = ',3^(LEVELS:0),'"))',sep=""))

[1] "expression(paste(3^4," = 81"))" "expression(paste(3^3," = 27"))" "expression(paste(3^2," = 9"))"
[4] "expression(paste(3^1," = 3"))"  "expression(paste(3^0," = 1"))"

expression(paste(3^4, "= 81"), paste(3^3, "= 27"), paste(3^2,
"= 9"), paste(3^1, "= 3"), paste(3^0, "= 1"))

mylabels <- parse(text=sprintf('paste(3^%d,' = %d')',LEVELS:0,3^(LEVELS:0)));
mylabels;
## expression(paste(3^4,' = 81'), paste(3^3,' = 27'), paste(3^2,' = 9'),
##     paste(3^1,' = 3'), paste(3^0,' = 1'))

c(
    expression(paste(3^4,"= 81")),
    expression(paste(3^3,"= 27")),
    expression(paste(3^2,"= 9")),
    expression(paste(3^1,"= 3")),
    expression(paste(3^0,"= 1"))
)

expression(
    paste(3^4,"= 81"),
    paste(3^3,"= 27"),
    paste(3^2,"= 9"),
    paste(3^1,"= 3"),
    paste(3^0,"= 1")
)

c(paste("expression(paste(3^",LEVELS:0,'," = ',3^(LEVELS:0),'"))',sep=""))

paste("expression(paste(3^",LEVELS:0,'," = ',3^(LEVELS:0),'"))',sep="")