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 A071587 #13 Jan 21 2020 20:39:06 %S A071587 1,9,18,927,1656,94095,144135,9692874,12764034,984024783,1044876843, %T A071587 90695018313,184635924282,9238285681452,16945429767822, %U A071587 946490231198502,1481588810203581,96566699618177661,121999692536490051,9802992767171580531,10882965095456675121 %N A071587 Powers of 9 written backwards. %H A071587 Robert Israel, <a href="/A071587/b071587.txt">Table of n, a(n) for n = 0..1046</a> %p A071587 revdigs:= proc(n) local L; %p A071587 L:= convert(n,base,10); %p A071587 add(L[-i]*10^(i-1),i=1..nops(L)) %p A071587 end proc: %p A071587 seq(revdigs(9^n),n=0..50); # _Robert Israel_, Jan 21 2020 %t A071587 IntegerReverse[9^Range[0,20]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 26 2018 *) %o A071587 (PARI) for(i=1,50,n=9^i; s=ceil(log(n)/log(10)); print1(sum(i=0,s,10^(s-i-1)*(floor(n/10^i)-10*floor(n/10^(i+1)))),",")) %K A071587 easy,nonn,base %O A071587 0,2 %A A071587 _Benoit Cloitre_, Jun 01 2002