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I've been searching since a few days the symbol of Napier's number (e).

It is a symbol of and with a cut on the inside similary to the double struck commands (\mathbb). I vaguely remember that there is a package, perhaps distributed by Wolfram Alfa in a .zip file, which it can to be used in LaTeX documents. Currently I have not been able to find it.

Here there is a ugly screenshot (edit: slightly better screenshot from Wolfram|Alpha):

enter image description here

Related question: Truncation of Napier’s number (e) to an amount of decimal digits of my choice

  • Marijn thank you very muchhhh for the edit my code. – Sebastiano Jan 19 at 21:25
  • Please! Wolframalpha's symbol is even worse than writing it upright. Don't do it, please. – egreg Jan 19 at 22:53
  • @egreg "Comandi comandante" :-). Just it was only a curiosity and don't worry I will do not it. – Sebastiano Jan 20 at 7:24
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It's ⅇ U+2147 (ⅇ in HTML) so should be available in in any font that has double struck italic lower case. So any font used with unicode-math or for pdftex for example the stix and stix2 packages will make it available.

Actually I don't see it in the stix2 package which is surprising, with unicode-math it is

enter image description here

\documentclass{article}

\usepackage{unicode-math}

\begin{document}

$ \mitBbbe^i $

\end{document}

That is latin modern but any OpenType math font will have this.

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  • I always thank you for your kindness as Marijn that Have edited my question and he has finded a best image. Some time ago I found a series of .zip files that connected to LaTeX but I can't find it no more. – Sebastiano Jan 19 at 21:25
  • I have seen (in fact) stix and stix2 package documentation and I have not finded it. – Sebastiano Jan 19 at 21:32
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    @Sebastiano if you have mathematica you can use these ctan.org/pkg/mathematica?lang=en but I don't think the fonts are generally available any more. But as always you should not worry about the exact character shape, use the font that matches your document. No point in using the mathematica fonts for just one character. – David Carlisle Jan 19 at 21:33
  • U+2147 should be in stix2; it's certainly in the copy of the reference table I kept when I left AMS, although the name in that table is still \itBbbe. \mitBbbe, as in unicode-fonts, is the agreed "correct" name. – barbara beeton Jan 19 at 21:46
  • I think it should be also a double-struck i for the imaginary unit following the Wolfram conventions: $𝕖^𝕚$ or $ⅇ^ⅈ$. And a double-struck differential d: $∫𝕖^x \, 𝕕x = 𝕖^x + c$ or $∫ⅇ^x \, ⅆx = 𝕖^x + c$ :) – user125730 Jan 19 at 21:47

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