a(n) = T(6,n), array T given by A047858.

Terms

a(0) =1a(1) =8a(2) =23a(3) =55a(4) =123a(5) =267a(6) =571a(7) =1211a(8) =2555a(9) =5371a(10) =11259a(11) =23547a(12) =49147a(13) =102395a(14) =212987a(15) =442363a(16) =917499a(17) =1900539a(18) =3932155a(19) =8126459a(20) =16777211a(21) =34603003a(22) =71303163a(23) =146800635a(24) =301989883a(25) =620756987a(26) =1275068411a(27) =2617245691a(28) =5368709115a(29) =11005853691