1, 4, 6, 18, 36, 80, 172, 360, 760, 1576, 3264, 6720, 13776, 28160, 57376, 116640, 236608, 479104, 968640, 1955712, 3944064, 7945856, 15993856, 32168448, 64656640, 129879040, 260759040, 523289088, 1049711616, 2104967168, 4219743232, 8456841216, 16944388096