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 A306661 #36 May 07 2019 11:31:18 %S A306661 1,11,13,17,19,101,103,107,109,113,121,127,131,137,139,149,151,157, %T A306661 163,167,173,179,181,191,193,197,199,1009,1013,1019,1021,1031,1033, %U A306661 1039,1049,1051,1061,1063,1069,1087,1091,1093,1097,1103,1109,1111 %N 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. %C A306661 All prime numbers whose first digit is 1 (A045707) have this property. %C A306661 The first composite numbers having this property are A307858: 121, 1111, 1207, ... %e A306661 14641 is such a number because its divisors are 1, 11, 121, 1331, 14641. %e A306661 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. %t A306661 Select[Range@1500,And@@(Last@#[[1]]==First@#[[2]]&/@Partition[IntegerDigits/@Divisors@#,2,1])&] %Y A306661 A307858 and A045707 are subsequences. %K A306661 nonn,base %O A306661 1,2 %A A306661 _Giorgos Kalogeropoulos_, May 05 2019