a(n) = 2*a(n-1) - a(n-2) - a(n-4) with a(0) = a(1) = 0, a(2) = 1, a(3) = 2.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =3a(5) =4a(6) =4a(7) =2a(8) =-3a(9) =-12a(10) =-25a(11) =-40a(12) =-52a(13) =-52a(14) =-27a(15) =38a(16) =155a(17) =324a(18) =520a(19) =678a(20) =681a(21) =360a(22) =-481a(23) =-2000a(24) =-4200a(25) =-6760a(26) =-8839a(27) =-8918a(28) =-4797a(29) =6084