Generalized Lucas numbers.

Terms

a(0) =1a(1) =0a(2) =6a(3) =7a(4) =28a(5) =54a(6) =135a(7) =286a(8) =627a(9) =1313a(10) =2730a(11) =5565a(12) =11212a(13) =22304a(14) =43911a(15) =85614a(16) =165490a(17) =317373a(18) =604296a(19) =1143054a(20) =2149074a(21) =4017950a(22) =7473180a(23) =13832910a(24) =25490115a(25) =46774448a(26) =85494900a(27) =155693873a(28) =282551856a(29) =511101624