a(n) = [ (2n+2)/(n-1) ] + [ (2n+4)/(n-2) ] + ... + [ (4n-2)/1 ].

Terms

a(0) =6a(1) =14a(2) =23a(3) =33a(4) =44a(5) =55a(6) =67a(7) =81a(8) =93a(9) =105a(10) =120a(11) =133a(12) =149a(13) =164a(14) =177a(15) =191a(16) =210a(17) =222a(18) =240a(19) =256a(20) =270a(21) =288a(22) =305a(23) =322a(24) =336a(25) =355a(26) =373a(27) =387a(28) =410a(29) =421