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 A217742 #12 Mar 23 2013 05:10:54 %S A217742 525,4725,34125,38325,269325,307125,2150925,2184525,2423925,2457525, %T A217742 17203725,17506125,19358325,19660725,137626125,137894925,139810125, %U A217742 140078925,154833525,155102325,157017525,157286325 %N A217742 Numbers n with the property that if the base-8 representation of n is read backwards, the result is 5*n. %e A217742 n = 525 (base 10) = 1015 (base 8). Reading this backwards we get 5101 (base 8) = 2625 (base 10) = 5*n, so 525 is in the sequence. %Y A217742 Cf. A241927, A223089. %K A217742 nonn,base %O A217742 1,1 %A A217742 _N. J. A. Sloane_, Mar 23 2013