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 A191561 #18 Jul 22 2025 12:09:48
%S A191561 2,4,8,4,2,10,2,16,26,4,2,28,2,4,8,16,2,28,2,16,8,4,2,64,32,4,80,16,2,
%T A191561 64,2,64,8,4,53,28,2,4,8,16,2,64,2,16,107,4,2,64,128,124,8,16,2,82,98,
%U A191561 88,8,4,2,136,2,4,134,64,32,64,2,16,8,184,2,136,2,4
%N A191561 a(n) = 2^n mod 3*n.
%H A191561 Vincenzo Librandi, <a href="/A191561/b191561.txt">Table of n, a(n) for n = 1..1000</a>
%t A191561 Table[PowerMod[2, n, 3 n], {n, 100}] (* _Vincenzo Librandi_, Jun 12 2016 *)
%o A191561 (Magma) [Modexp(2, n, 3*n): n in [1..100]]; // _Vincenzo Librandi_, Jun 12 2016
%o A191561 (PARI) a(n)=lift(Mod(2,3*n)^n) \\ _Charles R Greathouse IV_, Dec 27 2011
%Y A191561 Cf. A083528, A083529, A083530.
%K A191561 nonn,easy
%O A191561 1,1
%A A191561 _Vincenzo Librandi_, Jul 31 2011