a(n)=T(n,n+1), array T as in A049723.

Terms

a(0) =4a(1) =13a(2) =26a(3) =46a(4) =75a(5) =104a(6) =148a(7) =189a(8) =241a(9) =302a(10) =363a(11) =439a(12) =508a(13) =596a(14) =681a(15) =774a(16) =886a(17) =991a(18) =1107a(19) =1224a(20) =1344a(21) =1489a(22) =1622a(23) =1778a(24) =1919a(25) =2083a(26) =2248a(27) =2409a(28) =2605a(29) =2774