%I #4 Oct 22 2018 12:02:11
%S 1,1,5,14,36,84,174,337,613,1058,1749,2787,4304,6463,9476,13598,19140,
%T 26486,36079,48461,64263,84209,109160,140100,178144,224578,280871,
%U 348655,429780,526341,640642,775262,933082,1117259,1331289,1579031,1864697,2192905
%N Number of 7-element subsets of [n] whose sum is a triangular number.
%H Alois P. Heinz, <a href="/A320853/b320853.txt">Table of n, a(n) for n = 7..1000</a>
%Y Column k=7 of A284249.
%Y Cf. A000217.
%K nonn
%O 7,3
%A _Alois P. Heinz_, Oct 22 2018
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