a(n) = (1-2*n^2)^2.

Terms

a(0) =1a(1) =1a(2) =49a(3) =289a(4) =961a(5) =2401a(6) =5041a(7) =9409a(8) =16129a(9) =25921a(10) =39601a(11) =58081a(12) =82369a(13) =113569a(14) =152881a(15) =201601a(16) =261121a(17) =332929a(18) =418609a(19) =519841a(20) =638401a(21) =776161a(22) =935089a(23) =1117249a(24) =1324801a(25) =1560001a(26) =1825201a(27) =2122849a(28) =2455489a(29) =2825761