Number of 7-element subsets of [n] whose sum is a triangular number.

Terms

a(0) =1a(1) =1a(2) =5a(3) =14a(4) =36a(5) =84a(6) =174a(7) =337a(8) =613a(9) =1058a(10) =1749a(11) =2787a(12) =4304a(13) =6463a(14) =9476a(15) =13598a(16) =19140a(17) =26486a(18) =36079a(19) =48461a(20) =64263a(21) =84209a(22) =109160a(23) =140100a(24) =178144a(25) =224578a(26) =280871a(27) =348655a(28) =429780a(29) =526341