Convolution of 3^n and floor(n/2).

Terms

a(0) =0a(1) =0a(2) =1a(3) =4a(4) =14a(5) =44a(6) =135a(7) =408a(8) =1228a(9) =3688a(10) =11069a(11) =33212a(12) =99642a(13) =298932a(14) =896803a(15) =2690416a(16) =8071256a(17) =24213776a(18) =72641337a(19) =217924020a(20) =653772070a(21) =1961316220a(22) =5883948671a(23) =17651846024a(24) =52955538084a(25) =158866614264a(26) =476599842805