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 A165739 #6 Apr 20 2023 17:50:05 %S A165739 4,3,8,13,27,49,99,180,330,567,957,1546,2479,3865 %N A165739 The number of palindromic numbers which are the product of a number and its reversal with 2n-1 digits. %C A165739 Every palindromic numbers which is the product of a number and its reversal has an odd number of digits. %e A165739 a(1)=4 because there are 4 numbers matching the definition with one digit: 0*0=0; 1*1=1; 2*2=4; 3*3=9; %e A165739 a(2)=3 because there are 3 numbers with three digits: 11*11=121; 12*21=252; 22*22=484; %e A165739 a(3)=8 because there are 8 numbers with five digits: 101*101=10201; 111*111=12321; 121*121=14641; 102*201=20502; 112*211=23632; 122*221=26962; 202*202=40804; 212*212=44944; %Y A165739 Cf. A158642. %K A165739 nonn,base %O A165739 1,1 %A A165739 _Floris P. van Doorn_, Sep 25 2009