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 A133949 #13 Sep 16 2015 13:43:26
%S A133949 0,0,3,2,0,0,2,4,0,0,3,3,0,0,6,2,0,0,2,8,0,0,4,6,0,0,5,2,0,0,2,6,0,0,
%T A133949 10,3,0,0,8,4,0,0,2,8,0,0,4,7,0,0,3,2,0,0,6,6,0,0,5,5,0,0,8,4,0,0,2,3,
%U A133949 0,0,4,4,0,0,5,2,0,0,4,9,0,0,5,10,0,0,6,2,0,0,4,3,0,0,10,4,0,0,8,2,0,0,2,13
%N A133949 a(n) = the number of "non-isolated divisors" of n(n+1)/2. A positive divisor k of n is non-isolated if either k-1 or k+1 also divides n.
%C A133949 a(k) = 0 for k mod 4 == {1,2}. - _Ray Chandler_
%H A133949 Ray Chandler, <a href="/A133949/b133949.txt">Table of n, a(n) for n=1..10000</a>
%F A133949 a(n) = A063440(n) - A133950(n) = A132747(A000217(n)).
%t A133949 Table[Length[Select[Divisors[n*(n + 1)/2], If[ # > 1, Mod[n*(n + 1)/2, #*(# - 1)] == 0] || Mod[n*(n + 1)/2, #*(# + 1)] == 0 &]], {n, 1, 80}] (* _Stefan Steinerberger_, Nov 01 2007 *)
%Y A133949 Cf. A133947, A133950, A063440.
%K A133949 nonn
%O A133949 1,3
%A A133949 _Leroy Quet_, Sep 30 2007
%E A133949 More terms from _Stefan Steinerberger_, Nov 01 2007
%E A133949 Extended by _Ray Chandler_, Jun 23 2008