a(n) = T(2n-1,n), where T is the array in A026098.

Terms

a(0) =1a(1) =6a(2) =15a(3) =28a(4) =55a(5) =78a(6) =119a(7) =152a(8) =230a(9) =290a(10) =372a(11) =444a(12) =574a(13) =645a(14) =752a(15) =901a(16) =1062a(17) =1159a(18) =1273a(19) =1491a(20) =1606a(21) =1817a(22) =1992a(23) =2314a(24) =2522a(25) =2828a(26) =2987a(27) =3210a(28) =3270a(29) =3616