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 A137580 #18 May 04 2015 01:18:07
%S A137580 1,1,1,1,2,3,3,3,4,5,5,6,6,5,6,7,5,9,8,8,9,7,7,10,9,8,9,10,8,9,9,10,9,
%T A137580 10,10,10,10,10,9,10,10,9,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
%U A137580 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10
%N A137580 Number of distinct digits in decimal representation of n!.
%H A137580 Reinhard Zumkeller, <a href="/A137580/b137580.txt">Table of n, a(n) for n = 0..1000</a>
%H A137580 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>.
%F A137580 a(n) = A043537(A000142(n)).
%F A137580 a(n) < 10 iff A137579(n) = 0.
%F A137580 a(A182049(n)) < 10. - _Reinhard Zumkeller_, Apr 08 2012
%e A137580 n=12: 12! = 479001600 => a(12) = #{0,1,4,6,7,9} = 6.
%t A137580 Map[Length[Union[IntegerDigits[#]]] &, Table[n!, {n, 0, 79}]] (* _Geoffrey Critzer_, May 25 2013 *)
%o A137580 (Haskell)
%o A137580 import Data.List (nub, sort)
%o A137580 a137580 = length . nub . show . a000142
%o A137580 -- _Reinhard Zumkeller_, Apr 08 2012
%o A137580 (PARI) A137580(n)=#Set(digits(n!)) \\ _M. F. Hasler_, May 04 2015
%Y A137580 Cf. A137577, A137578.
%Y A137580 Cf. A034886.
%K A137580 nonn,base
%O A137580 0,5
%A A137580 _Reinhard Zumkeller_, Jan 27 2008