This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A307858 #21 May 05 2019 21:53:17 %S A307858 121,1111,1207,1331,1441,1661,1991,10201,11231,11341,11561,11671, %T A307858 11917,12001,12221,12661,12767,12881,12937,12991,13211,13231,13541, %U A307858 14201,14311,14531,14641,14971,15191,15251,15851,15961,16181,16291,16621,16841,17161,17281,17309,17611 %N 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. %e A307858 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. %t A307858 Select[Range@20000,PrimeQ@#==False&&And@@(Last@#[[1]]==First@#[[2]]&/@Partition[IntegerDigits/@Divisors@#,2,1])&] %Y A307858 A306661 contains all these numbers plus prime numbers starting with 1. %K A307858 nonn,base %O A307858 1,1 %A A307858 _Giorgos Kalogeropoulos_, May 05 2019