readseq: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/readseq - from package: readseq

You may install the required package with command apt-get install {package}

Error in other languages:
readseq: bevel nie gevind nie
readseq: comandă negăsită
readseq: comando não encontrado
readseq: commande introuvable
readseq: command not found
readseq: käsku ei ole
readseq: không tìm thấy lệnh
readseq: komanda nerasta
readseq: Kommando nicht gefunden.
readseq: kommandot finns inte
readseq: komut yok
readseq: nie znaleziono polecenia
readseq: níor aimsíodh an t-ordú
readseq: no se encontró la orden
readseq: no s'ha trobat l'ordre
readseq: opdracht niet gevonden
readseq: parancs nem található
readseq: perintah tidak ditemukan
readseq: príkaz nenájdený
readseq: příkaz nenalezen
readseq: команда не найдена
readseq: командата не е открита
readseq: 命令找不到
readseq: コマンドが見つかりません