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A224930 Numbers n such that n divides the concatenation of all divisors in descending order. 8
1, 561, 1703, 2883, 11623, 14721, 32431, 205119, 361767, 826471901, 3747204067, 17463443163, 404345080971, 573488405493 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Like A069872 but in descending order.

a(11) > 2*10^9. - Donovan Johnson, May 05 2013

a(15) > 10^12. - Giovanni Resta, May 10 2013

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

Divisors of 561 are 1, 3, 11, 17, 33, 51, 187, 561 and 5611875133171131 / 561 = 10003342483371.

Divisors of 1703 are 1, 13, 131, 1703 and 1703131131 / 1703 = 1000077.

MAPLE

with(numtheory); A224930:=proc(q) local a, b, c, d, f, k, n;

for n from 1 to q do a:=sort([op(divisors(n))]); b:=nops(a); c:=a[b];

  for k from 1 to b-1 do d:=c; f:=0; while d>0 do f:=f+1; d:=trunc(d/10); od;

  c:=c+a[k+1]*10^f; od; if type(c/n, integer) then print(n); fi;

od; end: A224930 (10^6); # Paolo P. Lava, May 02 2013

MATHEMATICA

Select[Range[10^6/2]*2-1, Mod[ FromDigits@ Flatten@ IntegerDigits[ Reverse@ Divisors@ #], #] == 0 &] (* Giovanni Resta, May 05 2013 *)

CROSSREFS

Cf. A069872.

Sequence in context: A131672 A321156 A227976 * A083732 A292367 A290805

Adjacent sequences:  A224927 A224928 A224929 * A224931 A224932 A224933

KEYWORD

nonn,base,more

AUTHOR

Paolo P. Lava, May 02 2013

EXTENSIONS

a(10) from Donovan Johnson, May 05 2013

a(11)-a(12) from Giovanni Resta, May 05 2013

a(13)-a(14) from Giovanni Resta, May 10 2013

STATUS

approved

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Last modified July 23 14:11 EDT 2019. Contains 325254 sequences. (Running on oeis4.)