A237605 -id:A237605 - cp's OEIS frontend

A278440 Numbers n such that A244112(n) | n.

22, 777, 4444, 68868, 200000, 303030, 333000, 333333, 555555, 660000, 660660, 666666, 700000, 2332200, 3131313, 4444400, 6060600, 7007000, 7700000, 9009790, 9656955, 9885585, 11517771, 14233221, 14331231, 14333110, 14411040, 15143331, 15233221, 15331231, 15333110

Offset: 1

Paolo P. Lava, Nov 25 2016

A244112(68868) = 3826 and 68868 / 3826 = 18.

Paolo P. Lava, Table of n, a(n) for n = 1..200

Cf. A237605, A244112, A278439, A278441.

with(numtheory): P:=proc(q) local a,b,c,d,j,k,n; for n from 1 to q do a:=sort(convert(n,base,10));
for k from 1 to trunc(nops(a)/2) do c:=a[k]; a[k]:=a[nops(a)-k+1]; a[nops(a)-k+1]:=c; od;  k:=1; b:=a[1]; c:=0;
for j from 2 to nops(a) do if a[j]=b then k:=k+1; else d:=10*k+b; c:=c*10^(ilog10(d)+1)+d; k:=1; b:=a[j]; fi; od;
d:=10*k+b; c:=c*10^(ilog10(d)+1)+d; if type(n/c,integer) then print(n); fi; od; end: P(10^99);

Select[Range[10^6], Divisible[#, FromDigits@ Flatten@ Map[IntegerDigits, DeleteCases[#, k_ /; First@ k == 0]] &@ Reverse@ MapIndexed[{#1, (First@ #2 - 1)} &, RotateRight@ DigitCount@ #]] &] (* Michael De Vlieger, Dec 12 2016 *)

A278441 Numbers n such that n | A244112(n).

Original entry on oeis.org

1, 2, 5, 10, 22, 26, 32, 62, 91, 330, 370, 519, 575, 710, 1060, 4055, 29377, 79554, 108690, 150320, 306440, 2510048, 3605570, 14233221, 14331231, 14333110, 14509410, 15143331, 15233221, 15331231, 15333110, 16143331, 16153331, 16233221, 16331231, 16333110, 17143331

Offset: 1

Paolo P. Lava, Nov 25 2016

The sequence is bounded. See comment in A278439.

			A244112(519) = 191511 and 191511 / 519 = 369.

Paolo P. Lava, List of terms and corresponding ratios for n <= 10^9.

Cf. A237605, A244112, A278439, A278440.

with(numtheory): P:=proc(q) local a,b,c,d,j,k,n; for n from 1 to q do a:=sort(convert(n,base,10));
for k from 1 to trunc(nops(a)/2) do c:=a[k]; a[k]:=a[nops(a)-k+1]; a[nops(a)-k+1]:=c; od;  k:=1; b:=a[1]; c:=0;
for j from 2 to nops(a) do if a[j]=b then k:=k+1; else d:=10*k+b; c:=c*10^(ilog10(d)+1)+d; k:=1; b:=a[j]; fi; od;
d:=10*k+b; c:=c*10^(ilog10(d)+1)+d; if type(c/n,integer) then print(n); fi; od; end: P(10^99);

A278439 Numbers k such that k | A047842(k).

Original entry on oeis.org

1, 2, 5, 22, 105, 188, 258, 327, 663, 15425, 16654, 27848, 40324, 80328, 481263, 10213223, 10311233, 10313314, 10313315, 10313316, 10313317, 10313318, 10313319, 21322314, 21322315, 21322316, 21322317, 21322318, 21322319, 31123314, 31123315, 31123316, 31123317

Offset: 1

Paolo P. Lava, Nov 22 2016

The sequence is bounded. Let us consider a k-digit number n in which all 10 numerals from 0 to 9 are equally distributed: there are k/10 0's, k/10 1's, etc. This is the best case in order to have a number with the greatest number of digits under the transform n -> A047842(n). The number of digits we get is 10 + 10*floor(log_10(k/10) + 1), which must be >= k. The inequality becomes log_10(k/10) >= k/10 - 2, which is solved by k <= 23.75... This means that no term of the sequence can have more than 23 digits.

			A237605(258) = 121518 and 121518/258 = 471.

Paolo P. Lava, List of terms and corresponding ratios for n <= 10^9.

Cf. A047842, A237605, A278440, A278441.

with(numtheory): P:=proc(q) local a,b,c,d,j,k,n; for n from 1 to q do
a:=sort(convert(n,base,10)); k:=1; b:=a[1]; c:=0; for j from 2 to nops(a) do
if a[j]=b then k:=k+1; else d:=10*k+b; c:=c*10^(ilog10(d)+1)+d; k:=1; b:=a[j]; fi; od;
d:=10*k+b; c:=c*10^(ilog10(d)+1)+d; if type(c/n,integer) then print(n); fi; od; end: P(10^10);

a(32) corrected by Sean A. Irvine, May 27 2025

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A278440 Numbers n such that A244112(n) | n.

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A278441 Numbers n such that n | A244112(n).

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A278439 Numbers k such that k | A047842(k).

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