a(1) = 4; for n > 1, a(n) = 5*a(n-1) + 5 - n.

Terms

a(0) =4a(1) =23a(2) =117a(3) =586a(4) =2930a(5) =14649a(6) =73243a(7) =366212a(8) =1831056a(9) =9155275a(10) =45776369a(11) =228881838a(12) =1144409182a(13) =5722045901a(14) =28610229495a(15) =143051147464a(16) =715255737308