This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A011543 #27 Jul 08 2025 02:26:33
%S A011543 2,27,271,2718,27182,271828,2718281,27182818,271828182,2718281828,
%T A011543 27182818284,271828182845,2718281828459,27182818284590,
%U A011543 271828182845904,2718281828459045,27182818284590452,271828182845904523,2718281828459045235,27182818284590452353,271828182845904523536
%N A011543 Decimal expansion of e truncated to n places.
%C A011543 a(n) <= A011544(n) <= a(n)+1. - _Danny Rorabaugh_, Mar 07 2015
%H A011543 Danny Rorabaugh, <a href="/A011543/b011543.txt">Table of n, a(n) for n = 0..999</a>
%F A011543 a(n) = floor(e*10^n).
%t A011543 Module[{nn=30,edgs},edgs=RealDigits[E,10,nn][[1]];Table[ FromDigits[ Take[ edgs, n]],{n,nn}]] (* _Harvey P. Dale_, Oct 04 2017 *)
%o A011543 (PARI) a(n) = floor(exp(1)*10^n); \\ _Michel Marcus_, Mar 08 2015
%o A011543 (Python)
%o A011543 from sympy import E
%o A011543 def a(n): return int(E*10**n)
%o A011543 print([a(n) for n in range(21)]) # _Michael S. Branicky_, Feb 27 2021
%Y A011543 Cf. A001113, A011544.
%Y A011543 Cf. A011545, A011547, A011549, A011551.
%K A011543 nonn,easy,base
%O A011543 0,1
%A A011543 _N. J. A. Sloane_