Sum of numbers that can be written as t*n + u*(n+1) for nonnegative integers t,u in exactly n ways.

Terms

a(0) =1a(1) =57a(2) =390a(3) =1510a(4) =4335a(5) =10311a(6) =21532a(7) =40860a(8) =72045a(9) =119845a(10) =190146a(11) =290082a(12) =428155a(13) =614355a(14) =860280a(15) =1179256a(16) =1586457a(17) =2099025a(18) =2736190a(19) =3519390a(20) =4472391a(21) =5621407a(22) =6995220a(23) =8625300a(24) =10545925a(25) =12794301a(26) =15410682a(27) =18438490a(28) =21924435a(29) =25918635