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 A090057 #3 Jun 08 2025 16:15:42 %S A090057 1050,1080,3105,5100,5400,7020,7030,9207,9801,10010,10050,10080,10098, %T A090057 10200,10206,20020,20160,20250,20304,20400,20500,20790,21000,21060, %U A090057 30015,30030,30105,30240,30420,30450,30600,35100,40040,40050 %N A090057 Numbers n divisible by exactly two nontrivial permutations (rearrangements) of the digits of n. %C A090057 Trivial permutations are identified as (1) permutation = n, or (2) when n mod 10=0, permutations of n's digits which result in shifting only trailing zeros to the most significant side of n where they drop off, such that permutation = n/10^z, where z <= the number of trailing zeros of n. So if n were 1809000, the following permutations would be excluded as trivial: 1809000, 0180900, 0018090, 0001809. %H A090057 C. Seggelin, <a href="http://www.plastereddragon.com/maths/asortdiv.htm">Numbers Divisible by Digit Permutations</a>. %e A090057 a(3)=3105 because 3105 is divisible by both 135 and 1035, two nontrivial permutations of 3105. a(8)=9207 because 9207 is divisible by both 279 and 297, two nontrivial permutations of 9207. %Y A090057 Cf. A090055, A090058, A090059, A090060, A090061. %K A090057 nonn,base %O A090057 1,1 %A A090057 _Chuck Seggelin_, Nov 21 2003