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 A119398 #7 Apr 03 2018 15:13:32 %S A119398 628425,824175,1340325,1422135,1495725,1729665,1845585,1853775, %T A119398 1916145,2001825,2015685,2040675,2045505,2091375,2165625,2220435, %U A119398 2226609,2264535,2333925,2360085,2365965,2379465,2465925,2474955,2499255,2511495 %N A119398 Odd numbers taking exactly 21 steps to reach 15 in A086793. %C A119398 Most terms are multiples of 5. In the first 130 terms, there only 19 non-multiples of 5: 2226609, 2556477, 3252249, 3496779, 3638439, 4060287, 4779621, 4821453, 5146713, 5313231, 5365899, 5504499, 5578419, 5738733, 5785857, 5845749, 6189183, 6222447, 6236769. %H A119398 Robert Israel, <a href="/A119398/b119398.txt">Table of n, a(n) for n = 1..500</a> %p A119398 f:= proc(n) option remember; local t; %p A119398 if kernelopts(level) > 460 then return FAIL fi; %p A119398 t:= add(convert(convert(d,base,10),`+`),d=numtheory:-divisors(n)); %p A119398 1+procname(t) %p A119398 end proc: %p A119398 f(15):= 0: %p A119398 f(1):= FAIL: %p A119398 Res:= NULL: count:= 0: %p A119398 for n from 1 by 2 while count < 100 do %p A119398 if f(n) = 21 then Res:= Res, n; count:= count+1 fi; %p A119398 od: %p A119398 Res; # _Robert Israel_, Apr 03 2018 %Y A119398 Cf. A086793, A119396-A119415. %K A119398 base,nonn %O A119398 1,1 %A A119398 _Zak Seidov_, May 18 2006 %E A119398 a(1)=628425 inserted by _Robert Israel_, Apr 03 2018