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 A110709 #31 Sep 08 2022 08:45:20
%S A110709 1,323,93749,1959551,46118407,1207959551,37661140520651,
%T A110709 1390911669927935,55123269399790045,2333521433367183359,
%U A110709 105094533691406249999,5017514388048998039551,13456471561751415850795007,751799469150919163867112019
%N A110709 Nonprimes of the form n*(n-1)^n - 1.
%C A110709 If n = 3, then 3*2^3 - 1 = 23 is prime, so 23 is not in this sequence.
%H A110709 Vincenzo Librandi, <a href="/A110709/b110709.txt">Table of n, a(n) for n = 1..100</a>
%e A110709 a(1) = 1 = 2*1^2 - 1.
%e A110709 a(2) = 323 = 4*3^4 - 1.
%t A110709 Select[Table[n (n - 1)^n - 1, {n, 2, 20}], ! PrimeQ[#] &] (* _Vincenzo Librandi_, Mar 22 2014 *)
%o A110709 (Magma) [a: n in [2..40] | not IsPrime(a) where a is n*(n-1)^n-1]; // _Vincenzo Librandi_, Jun 13 2011
%Y A110709 Cf. A191699, A191715.
%K A110709 nonn
%O A110709 1,2
%A A110709 _Juri-Stepan Gerasimov_, Jun 13 2011
%E A110709 Corrected and extended by _Vincenzo Librandi_, Jun 13 2011