Number of length 2+2 0..n arrays with no pair in any consecutive three terms totalling exactly n.

Terms

a(0) =2a(1) =12a(2) =68a(3) =208a(4) =534a(5) =1116a(6) =2120a(7) =3648a(8) =5930a(9) =9100a(10) =13452a(11) =19152a(12) =26558a(13) =35868a(14) =47504a(15) =61696a(16) =78930a(17) =99468a(18) =123860a(19) =152400a(20) =185702a(21) =224092a(22) =268248a(23) =318528a(24) =375674a(25) =440076a(26) =512540a(27) =593488a(28) =683790a(29) =783900