a(n) = n^8 - n^6 + n^4 - n^2 + 1.

Terms

a(0) =1a(1) =1a(2) =205a(3) =5905a(4) =61681a(5) =375601a(6) =1634221a(7) =5649505a(8) =16519105a(9) =42521761a(10) =99009901a(11) =212601841a(12) =427016305a(13) =810932305a(14) =1468297741a(15) =2551550401a(16) =4278255361a(17) =6951703105a(18) =10986053005a(19) =16936647121a(20) =25536159601a(21) =37737287281a(22) =54762727405a(23) =78163228705a(24) =109884542401