The Mathematica code is below
hello = Rasterize[
Graphics[{Text[
Style["\!\(\*SubscriptBox[\(\[ScriptT]\), \(\[ScriptN]\)]\)=\!\(\
\*SubscriptBox[\(\[ScriptT]\), \(1\)]\)+(\[ScriptN]-1)\[CenterDot]\
\[ScriptD]", Bold, 40]]}], "Image"]; text =
ColorNegate[ImagePad[ImageCrop[hello], 6, White]];
stack =
Image3D@Join[ConstantArray[text, 20],
ConstantArray[
ColorConvert[ConstantImage[1, ImageDimensions[text]], "RGB"],
5]]; ImageMesh[stack, Method -> "DualMarchingCubes"]
Export["text3.STL", %]
The author hasn't provided the model origin yet.