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 A320850 #4 Oct 22 2018 12:00:33 %S A320850 1,1,3,6,11,20,32,48,70,98,132,174,226,287,359,444,542,655,783,928, %T A320850 1092,1275,1479,1707,1957,2231,2534,2865,3225,3617,4040,4497,4993, %U A320850 5527,6098,6710,7363,8062,8810,9605,10447,11342,12291,13295,14358,15478,16658,17904 %N A320850 Number of 4-element subsets of [n] whose sum is a triangular number. %H A320850 Alois P. Heinz, <a href="/A320850/b320850.txt">Table of n, a(n) for n = 4..1000</a> %Y A320850 Column k=4 of A284249. %Y A320850 Cf. A000217. %K A320850 nonn %O A320850 4,3 %A A320850 _Alois P. Heinz_, Oct 22 2018