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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A062680 Composite numbers n such that every divisor (except 1) of n contains the digit 9. 2
1691, 2291, 3629, 5191, 5539, 5597, 6931, 7391, 7921, 7961, 8497, 8791, 9101, 9329, 9409, 9481, 9671, 9701, 10981, 10991, 11269, 13129, 13891, 14239, 15089, 15931, 15941, 16999, 17197, 17309, 17879, 17951, 17993, 18091, 18449, 18829, 18943 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..37.

EXAMPLE

7961 has divisors 19, 419 and 7961, all of which contain the digit 9

MATHEMATICA

fQ[n_] := Union[Drop[Last /@ Sort /@ IntegerDigits[ Divisors[ n]], 1]] == {9}; Select[ Range[ 19110], fQ[ # ] == True && ! PrimeQ[ # ] &] (* Zak Seidov and Robert G. Wilson v, May 17 2005 *)

fQ[n_, dgt_] := Union[ MemberQ[#, dgt] & /@ IntegerDigits@ Rest@ Divisors@ n][[1]]; Select[ Range[2, 19110], !PrimeQ[#] && fQ[#, 9] &] (* Robert G. Wilson v, Jun 11 2014 *)

CROSSREFS

Composite members of A062679.

Sequence in context: A020241 A065903 A204488 * A251291 A120564 A237533

Adjacent sequences:  A062677 A062678 A062679 * A062681 A062682 A062683

KEYWORD

base,easy,nonn

AUTHOR

Erich Friedman, Jul 04 2001

EXTENSIONS

Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, May 16 2007

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 18 20:22 EDT 2019. Contains 327181 sequences. (Running on oeis4.)