Convolution of 4^n and floor(n/2).

Terms

a(0) =0a(1) =0a(2) =1a(3) =5a(4) =22a(5) =90a(6) =363a(7) =1455a(8) =5824a(9) =23300a(10) =93205a(11) =372825a(12) =1491306a(13) =5965230a(14) =23860927a(15) =95443715a(16) =381774868a(17) =1527099480a(18) =6108397929a(19) =24433591725a(20) =97734366910a(21) =390937467650