list =
  {33.25, 33.5625, 33.875, 34.1875, 34.5, 34.8125, 35.125, 35.4375, 35.75,
   36.0625, 36.375, 36.6875, 37.}

list={33.25, 33.5625, 33.875, 34.1875, 34.5, 34.8125, 35.125, 35.4375, 35.75, 36.0625, 36.375, 36.6875, 37.}

fit = FindFormula[list]
(*32.9375 + 0.3125 #1 &*)

fit[Range[20]]
(*{33.25, 33.5625, 33.875, 34.1875, 34.5, 34.8125, 35.125, 35.4375, 35.75, 36.0625, 36.375, 36.6875, 37., 37.3125, 37.625, 37.9375, 38.25, 38.5625, 38.875, 39.1875}*)

RandomInteger[{0, 100}, 50]

RandomReal[{0, 100}, 50]