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 A173573 #9 May 31 2023 12:46:09 %S A173573 1,2,3,4,81,82,83,84 %N A173573 3-Factorions: equal to the sum of the triple factorials of their digits in base 10. %C A173573 Sequence is complete. - _Giovanni Resta_, Mar 21 2013 %e A173573 81 -> 8!!! + 1!!! = 8*5*2 + 1 = 80 + 1 = 81. %p A173573 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(1000,3); %t A173573 stfQ[n_]:=n==Total[Times@@Range[#,1,-3]&/@IntegerDigits[n]]; Select[Range[100],stfQ] (* _Harvey P. Dale_, May 31 2023 *) %Y A173573 Cf. A007661, A014080, A097653, A173574-A173577 %K A173573 easy,fini,full,nonn,base %O A173573 1,2 %A A173573 _Paolo P. Lava_ and _Giorgio Balzarotti_, Feb 22 2010