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 A069693 #8 Dec 05 2013 19:55:17
%S A069693 0,1,3,6,10,15,21,28,36,45,55,66,78,91,105,300,406,703,903,3003,4005,
%T A069693 8001
%N A069693 Triangular numbers with either no internal digits or all internal digits are 0.
%H A069693 Max Alekseyev, <a href="/A069693/a069693.txt">Proof of finiteness of A069693 - A069700</a>
%e A069693 The internal digits of 3003 are "00", which are both 0. 15 has no internal digits.
%t A069693 Do[ If[ Union[ Drop[ RotateLeft[ IntegerDigits[n(n + 1)/2]], -2]] == {0}, Print[n(n + 1)/2]], {n, 14, 2 10^6}]
%Y A069693 Cf. A069675-A069684, A069693-A069700.
%K A069693 nonn,base,fini,full
%O A069693 1,3
%A A069693 _Amarnath Murthy_, Apr 06 2002
%E A069693 Corrected by _Sascha Kurz_, Jan 02 2003