Create simple line graph, no data points with "o"'s, etc?

[pythonscript]

I'm trying to generate a simple line graph of the iterations of a given natural number n, of the collatz conjecture, by importing the data from a csv file. For example, n=27 yields the attached data (I can't upload csv, so it's a txt file instead). I want to create a line graph like the one wikipedia displays, here:

http://upload.wikimedia.org/wikipedi...6/Collatz5.svg

where the data points aren't marked by some large point of an "o" or something to that effect. However, this code is all I can come up with:

c <- read.csv("data_27.csv", head=TRUE, sep=",")

max_x = max(c$n)

max_y = max(c$Value)

plot_colors <- c("blue","red","forestgreen")

jpeg(filename="27.jpg", bg="white")

plot(c$n, c$Value, pch=46, col=plot_colors[1], xlim=c(0, max_x), ylim=c(0, max_y), axes=FALSE, ann=FALSE)
lines(c$Value, pch=46, lty=1, col=plot_colors[1])

axis(1, las=1, at=2*0:max_x)

axis(2, las=1, at=2000*0:max_y)

box()

title(main="Collatz Sequence: 27", col.main="blue", font.main=3)

title(xlab= "n", col.lab=rgb(0,0.5,0))

title(ylab= "Value", col.lab=rgb(0,0.5,0))

dev.off()

which generates the attached jpeg, in which the data points are very obvious and the whole graph looks somewhat ugly. Can anyone help me create a better graph?