Is there an equivalent of Pythons range(12) in C#?
You're looking for the Enumerable.Range method:
var mySequence = Enumerable.Range(0, 12);
Just to complement everyone's answers, I thought I should add that Enumerable.Range(0, 12); is closer to Python 2.x's xrange(12) because it's an enumerable.
If anyone requires specifically a list or an array:
Enumerable.Range(0, 12).ToList();
or
Enumerable.Range(0, 12).ToArray();
are closer to Python's range(12).