a(n) = sum of absolute-valued coefficients of (1+2*x-2*x^2)^n.

Terms

a(0) =1a(1) =5a(2) =17a(3) =73a(4) =273a(5) =881a(6) =3785a(7) =13081a(8) =48737a(9) =184321a(10) =632193a(11) =2526305a(12) =8854081a(13) =32077921a(14) =124093025a(15) =428178641a(16) =1638563969a(17) =5878561921a(18) =21469361537a(19) =82252171393a(20) =286863949025