[seqfan] Formula syntax from some computer programming language

[Alonso Del Arte]

Does anyone recognize this syntax?

a(0) = 1, a(n) = subs(x = 1, diff(1/(2-x), x$n)), n = 1, 2... - _Karol A.
Penson_, Nov 12 2001

I'm guessing it's something calculus, but the dollar sign is really
throwing me off. It comes from A142, the factorials, the formula field of
that entry also including Wolfram Mathematica syntax in a contribution from
Alex Adamchuk.

Al

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Alonso del Arte
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