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 A327435 #19 Nov 02 2019 02:53:04 %S A327435 9,999,99999,9999999,999969999,99999999999,9999998999999, %T A327435 999999999999999,99999999799999999,9999999997999999999, %U A327435 999999999999999999999,99999999999899999999999,9999999999999999999999999,999999999999979999999999999,99999999999999999999999999999,9999999999999996999999999999999 %N A327435 a(n) is the largest (2n+1)-digit palindrome that is the product of two numbers having an equal number of digits. %C A327435 A308803 is the union of this sequence and A327897. This sequence lists the terms of odd indices of A308803 as they seem to be easier to compute than terms of even indices of A308803 (the sequence A327897). %H A327435 Chai Wah Wu, <a href="/A327435/b327435.txt">Table of n, a(n) for n = 0..89</a> %F A327435 a(n) = A308803(2n+1). %F A327435 a(n) >= (2*10^n-1)(5*10^n+1) = 10^(2n+1)-3*10^n-1. If n is a term of A308983, then a(n) = 10^(2n+1)-3*10^n-1. %e A327435 a(0) = 9 = 3 * 3 %e A327435 a(1) = 999 = 27 * 37 %e A327435 a(2) = 99999 = 123 * 813 %e A327435 a(3) = 9999999 = 2151 * 4649 %e A327435 a(4) = 999969999 = 16667 * 59997 %e A327435 a(5) = 99999999999 = 194841 * 513239 %e A327435 a(6) = 9999998999999 = 2893921 * 3455519 %e A327435 a(7) = 999999999999999 = 11099889 * 90090991 %e A327435 a(8) = 99999999799999999 = 265412903 * 376771433 %e A327435 a(9) = 9999999997999999999 = 2441330309 * 4096127411 %e A327435 a(10) = 999999999999999999999 = 19845575559 * 50389065161 %e A327435 a(11) = 99999999999899999999999 = 345867517613 * 289128047323 %Y A327435 Cf. A002113, A308803, A308983, A327897. %K A327435 nonn,base %O A327435 0,1 %A A327435 _Chai Wah Wu_, Oct 03 2019