A306303 Numbers that appear in the concatenation in decreasing order of their aliquot parts.

95, 110, 220, 312, 330, 371, 432, 440, 510, 525, 550, 624, 660, 714, 770, 864, 880, 936, 990, 995, 1111, 2480, 4100, 5115, 5125, 5134, 5135, 5625, 6120, 6432, 6794, 8100, 8145, 9225, 9864, 9950, 9995, 10250, 11100, 11110, 12864, 15375, 16200, 20500, 22200, 22220

Offset

1,1

Comments

The first terms that appear in both the concatenations in increasing and decreasing order are 510, 550, 624, 714, 1111, 5625, 50100, 51020, 53125, 56250, 67134, ...

Links

Paolo P. Lava, Table of n, a(n) for n = 1..250

Example

Aliquot parts of 95 are 1, 5, 19 and their concatenation in decreasing order is 1951 where 95 appears.

Maple

with(numtheory): P:=proc(n) local a, b, k;
a:=sort([op(divisors(n) minus {n})]); b:=a[nops(a)];
for k from nops(a) by -1 to 2 do b:=b*10^(ilog10(a[k-1])+1)+a[k-1]; od;
if searchtext(convert(n, string), convert(b, string))>0
then n; fi; end: seq(P(i), i=2..22220);

Mathematica

Select[Range[23000], SequenceCount[Flatten[IntegerDigits/@Reverse[Most[Divisors[ #]]]], IntegerDigits[ #]]>0&] (* Harvey P. Dale, Nov 20 2023 *)

Crossrefs

Cf. A056538, A248323.

Sequence in context: A338601 A338582 A338581 * A181767 A331663 A046005

Adjacent sequences: A306300 A306301 A306302 * A306304 A306305 A306306

Keyword

nonn,base,easy

Author

Paolo P. Lava, Feb 05 2019

Status

approved