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 A104390 #29 Mar 14 2025 11:04:02 %S A104390 32,42,60,70,104,152,231,315,316,322,330,342,361,406,430,450,540,602, %T A104390 610,612,632,703,722,812,1016,1027,1029,1108,1162,1190,1246,1261,1304, %U A104390 1314,1316,1351,1406,1470,1510,1603,2013,2054,2065,2070,2071,2106,2114 %N A104390 2-Smith numbers. %H A104390 Amiram Eldar, <a href="/A104390/b104390.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from G. C. Greubel) %H A104390 Shyam Sunder Gupta, <a href="http://www.shyamsundergupta.com/smith.htm">Smith Numbers</a>. %H A104390 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 A104390 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 A104390 32 is a 2-Smith number because the sum of the digits of its prime factors, i.e., Sp (32) = Sp(2*2*2*2*2)= 2 + 2 + 2 + 2 + 2 = 10, which is equal to twice the digit sum of 32, i.e., 2*S(32) = 2*(3 + 2) = 10. %t A104390 d[n_]:=IntegerDigits[n]; tr[n_]:=Transpose[FactorInteger[n]]; Select[Range[2120],2Total[d[#]]==Total[d@tr[#][[1]]*tr[#][[2]],2]&] (* _Jayanta Basu_, Jun 04 2013 *) %Y A104390 Cf. A006753, A104391. %K A104390 nonn,base %O A104390 1,1 %A A104390 _Eric W. Weisstein_, Mar 04 2005 and _Shyam Sunder Gupta_, Mar 11 2005