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 A104390 2-Smith numbers. 4
 32, 42, 60, 70, 104, 152, 231, 315, 316, 322, 330, 342, 361, 406, 430, 450, 540, 602, 610, 612, 632, 703, 722, 812, 1016, 1027, 1029, 1108, 1162, 1190, 1246, 1261, 1304, 1314, 1316, 1351, 1406, 1470, 1510, 1603, 2013, 2054, 2065, 2070, 2071, 2106, 2114 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from G. C. Greubel) Shyam Sunder Gupta, Smith Numbers. Wayne L. McDaniel, The Existence of infinitely Many k-Smith numbers, Fibonacci Quarterly, Vol. 25, No. 1 (1987), pp. 76-80. EXAMPLE 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. MATHEMATICA 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 *) CROSSREFS Cf. A006753, A104391. Sequence in context: A159007 A114042 A302168 * A302639 A302431 A303201 Adjacent sequences:  A104387 A104388 A104389 * A104391 A104392 A104393 KEYWORD nonn,base AUTHOR Eric W. Weisstein, Mar 04 2005 and Shyam Sunder Gupta, Mar 11 2005 STATUS approved

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Last modified October 25 11:56 EDT 2020. Contains 338012 sequences. (Running on oeis4.)