With Ctrl+Shift+E you can check that :reals:
produces TemplateBox[{}, "Reals"]
. Then you can take a peek at its DisplayFunction
with:
CurrentValue[{StyleDefinitions, "Reals"}]
{ TemplateBoxOptionsDisplayFunction -> (StyleBox["\[DoubleStruckCapitalR]", ShowSyntaxStyles -> False,
FontFamily -> "Times"] &),
TemplateBoxOptionsInterpretationFunction -> ("Reals" &),
TemplateBoxOptionsTooltip -> Automatic}
So the answer to your question is the FontFamily
:
Style["\[DoubleStruckCapitalN]", FontFamily -> "Times"]
Update:
In addition to that it is worth mentioning PositiveIntegers
, NonNegativeIngeters
and all family of combinations of sign+domain.
So depending on context you can use :nnint:
or :pint:
for natural numbers:
Those TemplateBoxes
have additional benefit, they have interpretation so while Style["\[DoubleStruckCapitalR]", FontFamily -> "Times"]
looks nice, :reals:
looks nice and represents Reals
you can use with symbolic math.