a(n) = G_n(5), where G_n(k) is the Goodstein function defined in A266201.

Terms

a(0) =5a(1) =27a(2) =255a(3) =467a(4) =775a(5) =1197a(6) =1751a(7) =2454a(8) =3325a(9) =4382a(10) =5643a(11) =7126a(12) =8849a(13) =10830a(14) =13087a(15) =15637a(16) =18499a(17) =21691a(18) =25231a(19) =29137a(20) =33427a(21) =38119a(22) =43231a(23) =48781a(24) =54787a(25) =61267a(26) =68239a(27) =75721a(28) =83731a(29) =92287