Table[Count[Tuples[{1, 0}, n], {___, 1, 1, ___}], {n, 10}]
Table[Count[Tuples[{1, 0}, n], {___, 1, 1, ___}], {n, 10}]; FindGeneratingFunction[%, x]
Table[Count[Tuples[{1, 0}, n], {___, 1, 1, ___}], {n, 10}]; FindGeneratingFunction[%, x]; Table[Count[Tuples[{1, 0}, n], {___, 1, 1, ___}], {n, 20}] - CoefficientList[Series[%, {x, 0, 19}], x]