A307858 Composite numbers k with its divisors having the property that the last digit of every divisor is the same as the first digit of the next divisor.

121, 1111, 1207, 1331, 1441, 1661, 1991, 10201, 11231, 11341, 11561, 11671, 11917, 12001, 12221, 12661, 12767, 12881, 12937, 12991, 13211, 13231, 13541, 14201, 14311, 14531, 14641, 14971, 15191, 15251, 15851, 15961, 16181, 16291, 16621, 16841, 17161, 17281, 17309, 17611

Offset

1,1

Links

Table of n, a(n) for n=1..40.

Example

97663 is in the sequence because it is composite and its divisors, 1, 127, 769, 97663 have the property that the last digit of every divisor is the first digit of the next one.

Mathematica

Select[Range@20000, PrimeQ@#==False&&And@@(Last@#[[1]]==First@#[[2]]&/@Partition[IntegerDigits/@Divisors@#, 2, 1])&]

Crossrefs

A306661 contains all these numbers plus prime numbers starting with 1.

Sequence in context: A302561 A120353 A175983 * A329100 A208261 A036928

Adjacent sequences: A307855 A307856 A307857 * A307859 A307860 A307861

Keyword

nonn,base

Author

Giorgos Kalogeropoulos, May 05 2019

Status

approved