A306661 Numbers with chained divisors: Numbers k with divisors such that the last digit of every divisor is the same as the first digit of the next divisor.

1, 11, 13, 17, 19, 101, 103, 107, 109, 113, 121, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 1009, 1013, 1019, 1021, 1031, 1033, 1039, 1049, 1051, 1061, 1063, 1069, 1087, 1091, 1093, 1097, 1103, 1109, 1111

Offset: 1

Author

Giorgos Kalogeropoulos, May 05 2019

Keywords

• nonn
• base

Comments

All prime numbers whose first digit is 1 (A045707) have this property.

The first composite numbers having this property are A307858: 121, 1111, 1207, ...

Examples

			14641 is such a number because its divisors are 1, 11, 121, 1331, 14641.
Also, 90043 is in the sequence because its divisors are 1, 127, 709, 90043 and the last digit of every divisor is the first digit of the next one.
		

Crossrefs

A307858 and A045707 are subsequences.

Programs

Mathematica

Select[Range@1500,And@@(Last@#[[1]]==First@#[[2]]&/@Partition[IntegerDigits/@Divisors@#,2,1])&]