sequencer: 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/sequencer - from package: python-sardana

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

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