n/2 analog of Keith numbers.

Terms

a(0) =50a(1) =642a(2) =1284a(3) =1926a(4) =2292a(5) =5088a(6) =29828a(7) =42922a(8) =53046a(9) =95968a(10) =512050a(11) =1043160a(12) =1723714a(13) =14819056a(14) =154860206a(15) =159251186a(16) =752516578a(17) =946218018a(18) =54728972948