# [Pari/GP], 20 bytes

Takes the input as a list of digits.

    a->a*Colrev([1..#a])

[Try it online!][TIO-jenznvrs]

---

# [Pari/GP], 17 bytes

Takes the input as a polynomial. For example, `5*x^4 + 3*x^3 + 7*x^2 + x + 6` means `53716`.

    a->x=1;eval(a+a')

[Try it online!][TIO-jenzt70y]


[Pari/GP]: http://pari.math.u-bordeaux.fr/
[TIO-jenznvrs]: https://tio.run/##K0gsytRNL/ifpmCr8D9R1y5Ryzk/pyi1TCPaUE9POTFW839iQUFOpUaigq6dQkFRZl4JkKkE4igppGkkamrqKERHm@ooGOsomOsoGOoomMUCRUDYEEzoKBjBaKAiENNSRwGEoKIGyAgkZqajADTOBGwiUIthLNAJAA "Pari/GP – Try It Online"
[TIO-jenzt70y]: https://tio.run/##TYzBCsIwEER/ZejFJE3AJG0lSPsjorAHK4UioYjEr4@bUMHD8nZmdifStphHzDNGZDJTGu35/qZVUEsHmSnG9SMIZkLclueL16aIBrMgKTUuvUq3Di080zNPTMdMPIPGUcPqKhyjJk4V6TXCfhqqEUreawzs9qx/xd1e7NX/u73K/AU "Pari/GP – Try It Online"