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 A330336 #10 Dec 18 2019 10:58:42
%S A330336 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,105,106,107,108,109,20,21,22,23,
%T A330336 24,205,206,207,208,209,30,31,32,33,34,305,306,307,308,309,40,41,42,
%U A330336 43,44,405,406,407,408,409,50,51,52,53,54,505,506,507
%N A330336 A322131/2.
%H A330336 Rémy Sigrist, <a href="/A330336/b330336.txt">Table of n, a(n) for n = 0..10000</a>
%F A330336 a(n) >= n with equality iff all the digits of the decimal representation of n, except possibly the first one, are in the range 0...4. - _Rémy Sigrist_, Dec 18 2019
%p A330336 a:= n-> (s-> parse(cat(seq(parse(s[i])*2, i=1..length(s))))/2)(""||n):
%p A330336 seq(a(n), n=0..70); # _Alois P. Heinz_, Dec 18 2019
%o A330336 (PARI) a(n, base=10) = my (d=digits(n, base), v=0); for (i=1, #d, v = v*base^max(1, #digits(2*d[i], base)) + 2*d[i]); v/2 \\ _Rémy Sigrist_, Dec 18 2019
%Y A330336 Cf. A322131.
%K A330336 nonn,base
%O A330336 0,3
%A A330336 _N. J. A. Sloane_, Dec 17 2019