A240265 Numbers that divide the concatenation of their aliquot divisors, in ascending order.

1, 4, 15, 16, 255, 375, 495, 795, 1469, 3825, 9375, 28125, 66375, 67875, 234375, 249487, 286875, 309375, 337185, 450615, 590625, 628125, 1369125, 2390625, 2773125, 2781387, 3069375, 3706785, 4965309, 5859375, 12890625, 13539375, 26803125, 39607575, 62578125

Offset: 1

Author

Paolo P. Lava, Apr 03 2014

Keywords

• nonn
• base

Comments

The sequence is infinite, because it contains all the numbers of the form 3*5^(2k+1). - Giovanni Resta, Apr 03 2014

Examples

			Aliquot divisors of 1469 are 1, 13, 113. Their concatenation in ascending order is 113113 and 113113/1469 = 77.
		

Crossrefs

Cf. A069872, A224930.

Programs

Maple

with(numtheory);
T:=proc(t) local x,y; x:=t; y:=0; while x>0 do x:=trunc(x/10); y:=y+1; od; end:
P:=proc(q) local a,b,c,d,i,k,n;
for n from 2 to q do a:=sort([op(divisors(n))]); b:=a[nops(a)-1];
for i from nops(a)-2 by -1 to 1 do b:=b+a[i]*10^T(b); od;
if type(b/n,integer) then print(n); fi;
od; end: P(10^6);

Mathematica

Select[Range[6258*10^4],Divisible[FromDigits[Flatten[IntegerDigits/@ Most[ Divisors[ #]]]],#]&] (* Harvey P. Dale, Aug 21 2019 *)

Extensions

a(14)-a(34) from Giovanni Resta, Apr 03 2014

First term (a(1) = 1) prepended by Harvey P. Dale, Aug 21 2019