a(n) = (5*n^2 - 11*n + 8)/2.

Terms

a(0) =1a(1) =3a(2) =10a(3) =22a(4) =39a(5) =61a(6) =88a(7) =120a(8) =157a(9) =199a(10) =246a(11) =298a(12) =355a(13) =417a(14) =484a(15) =556a(16) =633a(17) =715a(18) =802a(19) =894a(20) =991a(21) =1093a(22) =1200a(23) =1312a(24) =1429a(25) =1551a(26) =1678a(27) =1810a(28) =1947a(29) =2089