Repeatedly extract every second and third line of a file with 3-line data blocks

Question

I have a file where I have data in 3-line sets. I want the 2nd and 3rd line from each set. How do I get that?

For an example from: [set no][no of line in set]

11
12
13
21
22
23
31
32
33

I want:

12
13
22
23
32
33

and so on.

I have tried a few options but have been unsuccessful.

Answer 1

With POSIX awk:

awk '!(FNR%3==1)' <file

With POSIX sed:

sed -e '1d;n;n;d' <file

With GNU sed:

sed -e '1~3d' <file