a(n) = T(7,n), array T given by A047858.

Terms

a(0) =1a(1) =9a(2) =26a(3) =62a(4) =138a(5) =298a(6) =634a(7) =1338a(8) =2810a(9) =5882a(10) =12282a(11) =25594a(12) =53242a(13) =110586a(14) =229370a(15) =475130a(16) =983034a(17) =2031610a(18) =4194298a(19) =8650746a(20) =17825786a(21) =36700154a(22) =75497466a(23) =155189242a(24) =318767098a(25) =654311418a(26) =1342177274a(27) =2751463418a(28) =5637144570a(29) =11542724602