A335905(n) + A335906(n).

Terms

a(0) =0a(1) =2a(2) =-2a(3) =4a(4) =-6a(5) =10a(6) =-14a(7) =22a(8) =-32a(9) =50a(10) =-74a(11) =112a(12) =-168a(13) =254a(14) =-380a(15) =572a(16) =-858a(17) =1288a(18) =-1932a(19) =2900