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 A173574 #5 Dec 15 2018 15:42:20 %S A173574 1,2,3,4,5,49 %N A173574 4-Factorions: equal to the sum of the quadruple factorials of their digits in base 10. %e A173574 49 -> 4!!!! + 9!!!! = 4 + 9*5 = 4 +45 = 49. %p A173574 P:=proc(n,m) local a,b,i,j,k,x,w; for i from 1 by 1 to n do a:=0; b:=0; w:=0; k:=i; while k>0 do w:=k-(trunc(k/10)*10); j:=w; x:=w-m; if w=0 then b:=1; else while x>0 do j:=j*x; x:=x-m; od; b:=j; fi; a:=a+b; k:=trunc(k/10); od; if a=i then lprint(i,a); fi; od; end: P(1000,4); %t A173574 qfd[n_]:=Times@@Range[n,1,-4]; Select[Range[50],Total[qfd/@ IntegerDigits[ #]] == #&] (* _Harvey P. Dale_, Dec 15 2018 *) %Y A173574 Cf. A007662, A014080, A097653, A173573, A173575-A173577 %K A173574 easy,fini,nonn,base %O A173574 1,2 %A A173574 _Paolo P. Lava_, Feb 22 2010