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 A068884 #10 Mar 22 2024 16:28:02 %S A068884 6,78,903,9870,96141,941878,9850141,98947278,985036305,9892547470, %T A068884 98585094741,989436909450,9898947258903,98969892923278, %U A068884 989872901298945,9898987276765450,98985850965876105,989898183850729896,9898969072503098503 %N A068884 Largest n-digit triangular number with property that digits alternate in parity, or 0 if no such number exists. %H A068884 Sean A. Irvine, <a href="/A068884/b068884.txt">Table of n, a(n) for n = 1..50</a> %e A068884 a(4) = 9870 is a term as 9, 8, 7 and 0 have odd and even parity alternately. %Y A068884 Cf. A068876, A030152, A068882, A068883. %K A068884 base,nonn %O A068884 1,1 %A A068884 _Amarnath Murthy_, Mar 19 2002 %E A068884 a(6)-a(19) from _Donovan Johnson_, Mar 11 2011