I have a FASTA-file like this:

>seqA 
AAAAAAAAAA
>seqB 
AAAAAAAAAA
>seqC 
TTTTTTTTTT
>seqD 
CCCCCCCCCC
>seqE 
CCCCCCCCCC
>seqF
AAAAAAAAAA

I'm recently learning SeqKit, and I've found that rename can append _N in the header based on the occurrence of the sequence, and also that rmdump can remove duplicates. Is it possible to have these two commands together? And if not, if I start appending _N, how do I make sure the highest number is kept when I remove duplicate sequences?

Maybe I'm not explaining myself well, and I'm all new to this, but basically, my end goal is preferably this:

>3 
AAAAAAAAAA
>1 
TTTTTTTTTT
>2 
CCCCCCCCCC

And if it's not possible to complete change the header, can the file be sorted by occurrence? Like this:

>seqA_3
AAAAAAAAAA
>seqD_2
CCCCCCCCCC
>seqC_1 
TTTTTTTTTT

And preferably it would be nice if the solution used SeqKit or another solution that is relatively low on memory, because my data set is very long.