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 A181721 #13 Aug 12 2015 03:28:14 %S A181721 1,1,1,1,1,1,1,1,1,101,1,18,24,101,34,101,42,45,48,51,6,1,14,101,21, %T A181721 24,27,65,32,101,23,72,1,101,101,101,29,22,24,26,28,22,8,1,12,14,42,8, %U A181721 6,21,3,49,67,27,1,101,75,32,5,51 %N A181721 The smallest number k such that the product k*n contains digit-reverse(n) as a substring. %C A181721 Here, the digit-reverse operation is defined to preserve trailing zeros: for n=10, digit-reverse(n) = 01 which is a substring of 101*10=1010, so a(10)=101. - _R. J. Mathar_, Nov 17 2010 %F A181721 a(n) = A181720(n)/n. - _Michel Marcus_, Aug 12 2015 %p A181721 A181721 := proc(n) nrev := ListTools[Reverse](convert(n,base,10)) ; for k from 1 do dgskn := convert(k*n,base,10) ; if verify(nrev,dgskn,sublist) then return k; end if; end do: end proc: %p A181721 seq(A181721(n),n=1..80) ; # _R. J. Mathar_, Nov 17 2010 %Y A181721 Cf. A181720. %K A181721 nonn,base %O A181721 1,10 %A A181721 _Claudio Meller_, Nov 17 2010