Number of 6-element subsets of [n] whose sum is a triangular number.

Terms

a(0) =1a(1) =1a(2) =4a(3) =11a(4) =26a(5) =55a(6) =106a(7) =190a(8) =321a(9) =518a(10) =804a(11) =1207a(12) =1763a(13) =2511a(14) =3502a(15) =4794a(16) =6447a(17) =8541a(18) =11163a(19) =14407a(20) =18382a(21) =23215a(22) =29040a(23) =36005a(24) =44284a(25) =54059a(26) =65529a(27) =78918a(28) =94466a(29) =112434