Multiple samplings and calculating Standard deviation and standard error of the Mean using a trend line

Assuming I have the following data:

df1<-rnorm(100,000, 20,5)

I want to get the following samples from df1 with 50 trials each:

C=( 25,50,100,200,300,400,500,600)

Next, I want to plot a trend line. In the trend line plot, the x-axis= Sample size and the y-axis is SD and SEM. Sorry, I was unable to draw the plot, but hopefully, my description is clear. Thanks for your help.