login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A104390 2-Smith numbers. 3
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

REFERENCES

McDaniel, W. L., "The Existence of infinitely Many k-Smith numbers", Fibonacci Quarterly, 25(1987), pp. 76-80.

LINKS

Table of n, a(n) for n=1..47.

S. S. Gupta, Smith Numbers.

EXAMPLE

32 is a 2-Smith number because 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: A167309 A159007 A114042 * A167528 A229115 A035112

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified December 22 02:57 EST 2014. Contains 252326 sequences.