a(1) = 5; for n > 1, a(n) = 6*a(n-1) + 6 - n.

Terms

a(0) =5a(1) =34a(2) =207a(3) =1244a(4) =7465a(5) =44790a(6) =268739a(7) =1612432a(8) =9674589a(9) =58047530a(10) =348285175a(11) =2089711044a(12) =12538266257a(13) =75229597534a(14) =451377585195