seqan_mason: 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/seqan_mason - from package: seqan-apps

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

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