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 A103125 #26 Mar 14 2025 09:51:36
%S A103125 2401,5010,7000,10005,10311,10410,10411,11060,11102,11203,12103,13002,
%T A103125 13021,13101,14001,14101,14210,20022,20121,20203,20401,21103,21112,
%U A103125 21120,21201,22040,22101,22201,23030,30003,30031,30320,31002,31101
%N A103125 4-Smith numbers.
%H A103125 Amiram Eldar, <a href="/A103125/b103125.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..600 from Harvey P. Dale)
%H A103125 Shyam Sunder Gupta, <a href="http://www.shyamsundergupta.com/smith.htm">Smith Numbers</a>.
%H A103125 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 A103125 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 A103125 2401 is a 4-Smith number because the sum of the digits of its prime factors, i.e., Sp(2401) = Sp(7*7*7*7) = 7 + 7 + 7 + 7 = 28, which is equal to 4 times the digit sum of 2401, i.e., 4*S(2401) = 4*(2 + 4 + 0 + 1) = 28.
%t A103125 sn4Q[n_]:=Module[{a=Total[Flatten[IntegerDigits/@(Table[First[#],{Last[ #]}]&/@FactorInteger[n])]],b=4Total[IntegerDigits[n]]},a==b] (* _Harvey P. Dale_, Oct 03 2011 *)
%Y A103125 Cf. A006753.
%K A103125 base,nonn
%O A103125 1,1
%A A103125 _Shyam Sunder Gupta_, Mar 16 2005