a(n) = sigma_3(2*n+1).

Terms

a(0) =1a(1) =28a(2) =126a(3) =344a(4) =757a(5) =1332a(6) =2198a(7) =3528a(8) =4914a(9) =6860a(10) =9632a(11) =12168a(12) =15751a(13) =20440a(14) =24390a(15) =29792a(16) =37296a(17) =43344a(18) =50654a(19) =61544a(20) =68922a(21) =79508a(22) =95382a(23) =103824a(24) =117993a(25) =137592a(26) =148878a(27) =167832a(28) =192080a(29) =205380