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 A109648 #15 Dec 31 2020 02:18:21
%S A109648 53,51,44,32,53,49,44,32,52,52,44,32,51,50,44,32,53,51,44,32,52,57,44,
%T A109648 32,52,52,44,32,51,50,44,32,53,50,44,32,53,50,44,32,52,52,44,32,51,50,
%U A109648 44,32,53,49,44,32,53,48,44,32,52,52,44,32,51,50,44,32,53,51,44,32,53
%N A109648 Sequence is its own ASCII representation (including commas and spaces).
%C A109648 Only possible values are 32, 44, 48, 49, 50, 51, 52, 53, 54, 55, 56 and 57 which make their first appearance at n: 3, 2, 53, 5, 13, 1, 8, 0, 853, 85, 213, 21. - _Robert G. Wilson v_, May 02 2006
%H A109648 <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%F A109648 a(4n) = 48 + floor( a(n)/10 ), a(4n+1) = 48 + remainder( a(n)/10 ), a(4n+2) = 44, a(4n+3) = 32.
%e A109648 a(0) = 53 = 0x35 --> '5'
%e A109648 a(1) = 51 = 0x33 --> '3'
%e A109648 a(2) = 44 = 0x2C --> ','
%e A109648 a(3) = 32 = 0x20 --> ' '
%e A109648 a(4) = 53 = 0x35 --> '5'
%e A109648 a(5) = 49 = 0x33 --> '1'
%e A109648 a(6) = 44 = 0x2C --> ','
%t A109648 a[0] = 53; a[1] = 51; a[n_] := Switch[Mod[n, 4], 0, 48 + Floor[a[n/4]/10], 1, 48 + Mod[a[(n - 1)/4], 10], 2, 44, 3, 32]; Table[a[n], {n, 0, 68}] (* _Robert G. Wilson v_, May 02 2006 *)
%o A109648 (PARI) (t=s->Vec(Vecsmall(Str(s))[2..-2]))(t(t(t(t([5]))))) \\ _M. F. Hasler_, Feb 02 2016
%Y A109648 Cf. A109733 is another version.
%K A109648 easy,nonn
%O A109648 0,1
%A A109648 _Andrew Weimholt_, Aug 05 2005