a(n) = (2n-2)^3 + (2n-2) - 1.

Terms

a(0) =-1a(1) =9a(2) =67a(3) =221a(4) =519a(5) =1009a(6) =1739a(7) =2757a(8) =4111a(9) =5849a(10) =8019a(11) =10669a(12) =13847a(13) =17601a(14) =21979a(15) =27029a(16) =32799a(17) =39337a(18) =46691a(19) =54909a(20) =64039a(21) =74129a(22) =85227a(23) =97381a(24) =110639a(25) =125049a(26) =140659a(27) =157517a(28) =175671a(29) =195169