a(n) = 2*a(n-1) + n^2, a(0) = 0.

Terms

a(0) =0a(1) =1a(2) =6a(3) =21a(4) =58a(5) =141a(6) =318a(7) =685a(8) =1434a(9) =2949a(10) =5998a(11) =12117a(12) =24378a(13) =48925a(14) =98046a(15) =196317a(16) =392890a(17) =786069a(18) =1572462a(19) =3145285a(20) =6290970a(21) =12582381a(22) =25165246a(23) =50331021a(24) =100662618a(25) =201325861a(26) =402652398a(27) =805305525a(28) =1610611834a(29) =3221224509