a(n) = 3*a(n-1) + 5*a(n-2), with a(0)=1, a(1)=5.

Terms

a(0) =1a(1) =5a(2) =20a(3) =85a(4) =355a(5) =1490a(6) =6245a(7) =26185a(8) =109780a(9) =460265a(10) =1929695a(11) =8090410a(12) =33919705a(13) =142211165a(14) =596232020a(15) =2499751885a(16) =10480415755a(17) =43940006690a(18) =184222098845a(19) =772366329985