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 A264688 #45 May 22 2025 10:21:44
%S A264688 0,1,1170,1528,9877,9886,9897,11535
%N A264688 The decimal digits of n appear n times in the decimal representation of n!.
%C A264688 There are no more terms up to n=21000, checked using the Python program below.
%C A264688 a(9) > 200000. - _Dana Jacobsen_, Jan 03 2016
%e A264688 1170 belongs to this sequence because the digits 1, 7 and 0 appear 1170 times in total in the decimal representation of 1170!.
%e A264688 0! = 1, which contains no zeros, so 0 is a term.
%o A264688 (Python)
%o A264688 from math import factorial
%o A264688 def in_a(n):
%o A264688 f = str(factorial(n))
%o A264688 s = set(str(n))
%o A264688 return sum(f.count(d) for d in s)==n
%o A264688 (Perl) use ntheory ":all"; sub is_a264688 { my $n = shift; $n == eval "factorial($n) =~ tr/[$n]//"; } # _Dana Jacobsen_, Jan 03 2016
%K A264688 nonn,base,more
%O A264688 1,3
%A A264688 _Christian Perfect_, Jan 03 2016