a(0) = 1; a(n) = (11*n^2 - 9*n + 4)/2 for n>0.

Terms

a(0) =1a(1) =3a(2) =15a(3) =38a(4) =72a(5) =117a(6) =173a(7) =240a(8) =318a(9) =407a(10) =507a(11) =618a(12) =740a(13) =873a(14) =1017a(15) =1172a(16) =1338a(17) =1515a(18) =1703a(19) =1902a(20) =2112a(21) =2333a(22) =2565a(23) =2808a(24) =3062a(25) =3327a(26) =3603a(27) =3890a(28) =4188a(29) =4497