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A221697 Numbers n such that largest digit of all divisors of n is 2. 2
2, 22, 121, 202, 211, 1021, 1201, 2011, 2111, 2221, 2222, 10201, 10211, 12011, 12101, 12211, 12221, 20011, 20021, 20101, 20201, 20222, 21001, 21011, 21101, 21121, 21211, 21221, 22111, 22121, 101021, 101221, 102001, 102101, 102121, 110221, 111121, 111211, 111221, 112111, 112121 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that largest digit of concatenation of all divisors (A037278) of n is 2.

Numbers n such that A209928(n) = 2.

Union of A221698 and A106100.

LINKS

Table of n, a(n) for n=1..41.

EXAMPLE

Number 10201 is in sequence because largest digit of all divisors of 10201 (1, 101, 10201) is 2.

MAPLE

isA221697 := proc(n)

      local dgs, d;

      dgs := {} ;

    for d in numtheory[divisors](n) do

        dgs := dgs union convert(convert(d, base, 10), set) ;

    end do:

    if max(op(dgs)) = 2 then

        true;

    else

        false;

    end if;

end proc:

for n from 2 to 112121 do

    if isA221697(n) then

        printf("%d, ", n) ;

    end if;

end do: # R. J. Mathar, Jan 30 2013

MATHEMATICA

Select[Range[115000], Max[Flatten[IntegerDigits/@Divisors[#]]]==2&] (* Harvey P. Dale, Dec 15 2014 *)

CROSSREFS

Cf. A209928 (largest digit of all divisors of n), A221698.

Sequence in context: A325948 A216801 A083833 * A292452 A292732 A255866

Adjacent sequences:  A221694 A221695 A221696 * A221698 A221699 A221700

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Jan 22 2013, corrected Jan 29 2013

STATUS

approved

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Last modified September 22 11:29 EDT 2020. Contains 337289 sequences. (Running on oeis4.)