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 A068641 #9 Aug 11 2024 14:41:34 %S A068641 1,55,171,3003,15051,617716,1269621,35133153,178727871,1264114621, %T A068641 13953435931,0,1313207023131,19895044059891,114401848104411, %U A068641 1250444114440521,11121736463712111,357961407704169753 %N A068641 Smallest n-digit palindromic triangular number, or 0 if no such number exists. %H A068641 P. De Geest, <a href="https://www.worldofnumbers.com/em_alltria.htm">Exhaustive list of Palindromic Triangulars</a> %e A068641 a(4) = 3003 = 77*78/2 is the smallest 4-digit palindromic triangular number. %e A068641 a(12) = 0 as no 12-digit palindromic triangular number exists. %Y A068641 Cf. A068642, A068643, A068644, A000217, A003098, A008509, A008510, A054263. %K A068641 base,nonn %O A068641 1,2 %A A068641 _Amarnath Murthy_, Feb 28 2002 %E A068641 Edited by _Patrick De Geest_, Mar 24 2002