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 A083530 #19 Oct 18 2018 04:14:49
%S A083530 1,1,1,1,7,1,7,1,1,9,7,1,7,21,13,1,7,1,7,1,7,5,7,1,7,49,1,49,7,49,7,1,
%T A083530 13,49,63,1,7,49,31,1,7,49,7,25,37,49,7,1,49,49,37,9,7,1,43,49,1,49,7,
%U A083530 1,7,49,91,1,37,37,7,89,67,49,7,1,7,49,43,121,105,25,7,1,1,49,7,49,147,49
%N A083530 a(n) = 7^n mod (2*n).
%H A083530 Vincenzo Librandi, <a href="/A083530/b083530.txt">Table of n, a(n) for n = 1..1000</a>
%e A083530 For n = 5, a(5) = 7 because 7^5 = 16807 = 1680*10 + 7, that is 7^5 == 7 (mod 2*5).
%t A083530 Table[Mod[7^w, 2*w], {w, 1, 100}]
%o A083530 (PARI) a(n)=lift(Mod(7,2*n)^n) \\ _Charles R Greathouse IV_, Oct 03 2016
%Y A083530 Cf. A000079, A000244, A000351, A000420, A082511, A083528, A083529.
%K A083530 easy,nonn
%O A083530 1,5
%A A083530 _Labos Elemer_, Apr 30 2003