gp2c: 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/gp2c - from package: pari-gp2c

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

Error in other languages:
gp2c: bevel nie gevind nie
gp2c: comandă negăsită
gp2c: comando não encontrado
gp2c: commande introuvable
gp2c: command not found
gp2c: käsku ei ole
gp2c: không tìm thấy lệnh
gp2c: komanda nerasta
gp2c: Kommando nicht gefunden.
gp2c: kommandot finns inte
gp2c: komut yok
gp2c: nie znaleziono polecenia
gp2c: níor aimsíodh an t-ordú
gp2c: no se encontró la orden
gp2c: no s'ha trobat l'ordre
gp2c: opdracht niet gevonden
gp2c: parancs nem található
gp2c: perintah tidak ditemukan
gp2c: príkaz nenájdený
gp2c: příkaz nenalezen
gp2c: команда не найдена
gp2c: командата не е открита
gp2c: 命令找不到
gp2c: コマンドが見つかりません