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 A086078 #11 May 05 2024 19:32:07 %S A086078 0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0, %T A086078 0,0,0,1,1,1,0,0,0,0,0,0,0,0,1,0,1,0,1,0,0,0,0,0,1,2,0,0,0,0,0,0,0,1, %U A086078 0,0,0,0,0,1,2,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0,0,1,1,0,0,0,1,0,0,0,0,0,0,0 %N A086078 Number of 7's in decimal expansion of triangular number n(n+1)/2. %H A086078 Paolo Xausa, <a href="/A086078/b086078.txt">Table of n, a(n) for n = 0..10000</a> %t A086078 DigitCount[Accumulate[Range[0, 100]], 10, 7] (* _Paolo Xausa_, May 05 2024 *) %Y A086078 Cf. 0's A086071, 1's A086072, 2's A086073, 3's A086074, 4's A086075, 5's A086076, 6's A086077, 8's A086079, 9's A086080. %Y A086078 Cf. A000217. %K A086078 base,nonn %O A086078 0,60 %A A086078 _Jason Earls_, Jul 08 2003