Understandable, though it would have also made the first order recurrence relationships more accurate, e.g. annualized interest on an initial balance:

    accumulate(repeat(None), lambda: bal, _: bal*1.05, initializer=1000)

vs. artificially repeating 1000:

    accumulate(repeat(1000), lambda: bal, _: bal*1.05)

Or, if the initialiser is expensive:

    accumulate(chain([1000], repeat(None)), lambda: bal, _: bal*1.05)