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 A008903 #12 Jul 08 2025 01:23:53
%S A008903 100,50,25,74,37,110,55,164,82,41,122,61,182,91,272,136,68,34,17,50,
%T A008903 25,74,37,110,55,164,82,41,122,61,182,91,272,136,68,34,17,50,25,74,37,
%U A008903 110,55,164,82,41,122,61,182,91
%N A008903 x->x/2 if x even, x->3x-1 if x odd.
%D A008903 R. K. Guy, Unsolved Problems in Number Theory, E16.
%H A008903 <a href="/index/Rec#order_18">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).
%F A008903 a(n)=A003124(n), n>0. - _R. J. Mathar_, May 26 2008
%t A008903 NestList[If[EvenQ[#],#/2,3#-1]&,100,120] (* or *) PadRight[{100},120,{17,50,25,74,37,110,55,164,82,41,122,61,182,91,272,136,68,34}] (* _Harvey P. Dale_, May 20 2021 *)
%K A008903 nonn
%O A008903 0,1
%A A008903 _N. J. A. Sloane_