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 A104391 #32 Mar 14 2025 11:04:10
%S A104391 402,510,700,1113,1131,1311,2006,2022,2130,2211,2240,3102,3111,3204,
%T A104391 3210,3220,4031,4300,4410,5310,6004,6100,6300,7031,7120,9000,10034,
%U A104391 10125,10206,10251,10304,10413,10521,10612,10800,11033,11111,11114,11116,11121,11141
%N A104391 3-Smith numbers.
%H A104391 Amiram Eldar, <a href="/A104391/b104391.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1500 from G. C. Greubel)
%H A104391 Shyam Sunder Gupta, <a href="http://www.shyamsundergupta.com/smith.htm">Smith numbers</a>.
%H A104391 Shyam Sunder Gupta, <a href="https://doi.org/10.1007/978-981-97-2465-9_4">Smith Numbers</a>, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 4, 127-157.
%H A104391 Wayne L. McDaniel, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Scanned/25-1/mcdaniel.pdf">The Existence of infinitely Many k-Smith numbers</a>, Fibonacci Quarterly, Vol. 25, No. 1 (1987), pp. 76-80.
%e A104391 402 is a 3-Smith number because the sum of the digits of its prime factors, i.e., Sp(402) = Sp(2*3*67)= 2 + 3 + 6 + 7 = 18, which is equal to 3 times the digit sum of 402, i.e., 3*S(402) = 3*(4 + 0 + 2) = 18.
%t A104391 Select[Range[12000],Total[Flatten[IntegerDigits/@Table[#[[1]],{#[[2]]}]&/@ FactorInteger[#]]]/Total[IntegerDigits[#]]==3&] (* _Harvey P. Dale_, Feb 19 2013 *)
%Y A104391 Cf. A006753, A104390.
%K A104391 nonn,base
%O A104391 1,1
%A A104391 _Eric W. Weisstein_, Mar 04 2005 and _Shyam Sunder Gupta_, Mar 11 2005