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 A158642 #17 Aug 24 2025 05:50:54 %S A158642 0,1,4,9,121,252,484,10201,12321,14641,20502,23632,26962,40804,44944, %T A158642 1002001,1113111,1226221,1234321,1357531,2005002,2126212,2216122, %U A158642 2249422,2347432,2429242,4008004,4229224,100020001,102030201,104060401,110131011,112242211,114373411,120262021 %N A158642 Palindromic numbers which are the product of a number k and its reversal (k written backwards). %C A158642 Apart from 3 which produces 9 (3*3), all the other numbers k which satisfy the definition are formed by digits 0, 1 and 2 only. Subset of A002113. %C A158642 Every term has an odd number of digits. - _Floris P. van Doorn_, Sep 25 2009 %H A158642 Floris P. van Doorn, <a href="/A158642/b158642.txt">Table of n, a(n) for n=0..10126</a> (terms < 10^27). %e A158642 0*0=0; 1*1=1; 2*2=4; 3*3=9; 11*11=121; 12*21=252; 22*22=484; 101*101=10201; 102*201=20502; etc. %Y A158642 Cf. A002113. %K A158642 nonn,easy,base,changed %O A158642 0,3 %A A158642 _Paolo P. Lava_ and _Giorgio Balzarotti_, Mar 23 2009 %E A158642 Corrected by _Floris P. van Doorn_, Sep 25 2009