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 A127634 #11 Sep 08 2022 08:45:29
%S A127634 0,1,4,16,54,178,565,1770,5493,16927,51901,158533,482802,1466859,
%T A127634 4448104,13467249,40720970,122994566,371156622,1119161662,3372427789,
%U A127634 10156591942,30573367574,91993546765,276703494365,832023918335,2501142914874,7516883840470
%N A127634 a(n) = 3^(n-1) - ceiling(n^n/n!).
%C A127634 Theorem: 3^(n-1) > n^n/n! for n >= 3.
%D A127634 D. S. Mitrinovic, Analytic Inequalities, Springer-Verlag, 1970; p. 193, 3.1.21.
%H A127634 Robert Israel, <a href="/A127634/b127634.txt">Table of n, a(n) for n = 1..2094</a>
%p A127634 seq(3^(n-1)-ceil(n^n/n!),n=1..50); # _Robert Israel_, Jul 06 2017
%t A127634 Table[3^(n-1) - Ceiling[n^n / n!], {n, 30}] (* _Vincenzo Librandi_, Jul 06 2017 *)
%o A127634 (PARI) a(n) = 3^(n-1) - ceil(n^n/n!); \\ _Michel Marcus_, Jul 06 2017
%o A127634 (Magma) [3^(n-1)-Ceiling(n^n/Factorial(n)): n in [1..30]]; // _Vincenzo Librandi_, Jul 06 2017
%Y A127634 Cf. A000244, A073225.
%K A127634 nonn
%O A127634 1,3
%A A127634 _N. J. A. Sloane_, Apr 03 2007