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 A110728 #25 Dec 12 2020 22:03:28
%S A110728 1,1,2,6,24,30,18,63,72,81,90,99,216,117,126,135,144,153,162,171,180,
%T A110728 189,396,414,216,225,234,243,252,261,270,279,576,594,612,315,324,333,
%U A110728 342,351,360,369,756,774,792,810,414,423,432,441,450,459,936,954,972
%N A110728 Digital factorial: a(0) = 1, a(n) = n * (the sum of the digits of a(n-1)).
%H A110728 Colin Barker, <a href="/A110728/b110728.txt">Table of n, a(n) for n = 0..1000</a>
%e A110728 a(4) = 24, a(5) = 5*(2+4) = 30, a(6) = 6*3 = 18.
%p A110728 a:= proc(n) option remember; `if`(n=0, 1,
%p A110728 n*add(i, i=convert(a(n-1), base, 10)))
%p A110728 end:
%p A110728 seq(a(n), n=0..60); # _Alois P. Heinz_, Dec 12 2020
%t A110728 DigitSum[n_, 10] := Total[IntegerDigits[n, 10]]; A110728[0] := 1; A110728[n_] := A110728[n] = n*DigitSum[A110728[n - 1], 10]; Table[A110728[n], {n, 0, 50}] (* _G. C. Greubel_, Sep 06 2017 *)
%o A110728 (PARI) s=vector(1001, n, 1); for(n=2, #s, s[n]=(n-1)*sumdigits(s[n-1])); s \\ _Colin Barker_, Nov 20 2014
%Y A110728 Cf. A000142, A007953, A089718, A110729.
%K A110728 base,easy,nonn
%O A110728 0,3
%A A110728 _Amarnath Murthy_, Aug 09 2005
%E A110728 a(22) and a(32) corrected, name clarified, and more terms added by _Colin Barker_, Nov 20 2014