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 A069172 #13 Nov 16 2017 15:52:22
%S A069172 1,105,3,435,28,6,5995,589598998999878
%N A069172 Smallest triangular number such that arithmetic mean of its digits = n (sum of the digits = n times the number of digits).
%C A069172 Because A045914 is complete, this sequence is complete. - _Robert G. Wilson v_, Oct 30 2013
%t A069172 Do[k = 1; While[ Apply[ Plus, IntegerDigits[k(k + 1)/2]] != n*Floor[ Log[10, k(k + 1)/2] + 1], k++ ]; Print[k(k + 1)/2], {n, 1, 7}]
%Y A069172 Cf. A069790.
%K A069172 base,fini,full,nonn
%O A069172 1,2
%A A069172 _Robert G. Wilson v_, Apr 09 2002
%E A069172 a(8) from _Donovan Johnson_, Mar 30 2010