MathDB

For an integer

n

with

b

digits, let a subdivisor of

n

be a positive number which divides a number obtained by removing the

r

leftmost digits and the

l

rightmost digits of

n

for nonnegative integers

r,l

with

r+l<b

(For example, the subdivisors of

143

are

1

2

3

4

7

11

13

14

43

, and

143

). For an integer

d

, let

A_d

be the set of numbers that don't have

d

as a subdivisor. Find all

d

, such that

A_d

is finite.

Problem Statement