N-Bonnaci sequence calculator
Algorithm

Looks like you are doing too much. The recurrence can be greatly simplified:

\$a_{n} = a_{n-1} + a_{n-2} + \cdot\cdot\cdot + a_{n-k+1} + a_{n-k}\$, and

\$a_{n+1} = a_{n} + a_{n-1} + \cdot\cdot\cdot + a_{n-k+1}\$, so

\$a_{n+1} = a_{n} + (a_{n-1} + \cdot\cdot\cdot + a_{n-k+1}) = a_{n} + (a_{n} - a_{n-k})\$

meaning that the next k-bonacchi number is just

  sequence[n+1] = 2*sequence[n] + sequence[n-k]

Naming

Honestly, names like sqnceItratr and crrntVlue are more than unreadable. Don't abbreviate so aggressively. In this particular case I'd say that n fits much better than sqnceItratr.
Separation of concerns

calculateSequence initialize the sequence and produces the rest of it in a single call. It doesn't look right. I recommend to split the solution in initialize, and compute_next calls, along the lines of

sequence = initialize(N)
for n in range(N, limit):
    value = compute_next(sequence, N)
    sequence.append(value)