blastclust: 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/blastclust - from package: blast2

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

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