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 A138616 #11 Sep 08 2022 08:45:33
%S A138616 0,1,1,7,1,7,17,119,193,327,753,1175,2081,6375,3665,9271,32129,28295,
%T A138616 66993,206807,923361,1220647,2253073,7382903,9737281,1052103,40919153,
%U A138616 17998615,125990305,345061223,804815825,265001655,1855011585,4395146503,4996221745
%N A138616 a(n) = 7^n mod 2^n.
%H A138616 Vincenzo Librandi, <a href="/A138616/b138616.txt">Table of n, a(n) for n = 0..1000</a>
%t A138616 Table[PowerMod[7,n,2^n],{n,0,40}] (* _Harvey P. Dale_, Mar 19 2013 *)
%o A138616 (Magma) [7^n mod 2^n: n in [0..35]]; // _Vincenzo Librandi_, Jun 03 2011
%K A138616 nonn
%O A138616 0,4
%A A138616 _N. J. A. Sloane_, May 20 2008