If n < 8 then A058966(n), else n*2^(n - 3) - 2*n - 50.

Terms

a(0) =1a(1) =2a(2) =10a(3) =30a(4) =78a(5) =190a(6) =508a(7) =1210a(8) =2744a(9) =6070a(10) =13236a(11) =28594a(12) =61360a(13) =130990a(14) =278444a(15) =589738a(16) =1245096a(17) =2621350a(18) =5504932a(19) =11534242a(20) =24117152a(21) =50331550a(22) =104857500a(23) =218103706a(24) =452984728a(25) =939523990a(26) =1946156948a(27) =4026531730a(28) =8321499024