login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A103123 1/4-Smith numbers. 3
19899699, 36969999, 36999699, 39699969, 39999399, 39999993, 66699699, 66798798, 67967799, 67987986, 69759897, 69889389, 69966699, 69996993, 76668999, 79488798, 79866798, 85994799, 86686886, 89769759, 89866568 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
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
19899699 is a 4^(-1) Smith number because the digit sum of 19899699, i.e., S(19899699) = 1 + 9 + 8 + 9 + 9 + 6 + 9 + 9 = 60, which is equal to 4 times the sum of the digits of its prime factors, i.e., 4*Sp(19899699) = 4*Sp (3*2203*3011) = 4*(3 + 2 + 2 + 0 + 3 + 3 + 0 + 1 + 1) = 15.
MATHEMATICA
digSum[n_] := Plus @@ IntegerDigits[n]; qSmithQ[n_] := CompositeQ[n] && 4 * Plus @@ (Last@# * digSum[First@#] & /@ FactorInteger[n]) == digSum[n]; Select[Range[10^8], qSmithQ] (* Amiram Eldar, Aug 23 2020 *)
CROSSREFS
Cf. A006753.
Sequence in context: A284101 A303448 A251513 * A107618 A050945 A251458
KEYWORD
base,nonn
AUTHOR
Shyam Sunder Gupta, Mar 16 2005
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 21 03:13 EST 2024. Contains 370219 sequences. (Running on oeis4.)