a(n)=5*a(n-1)+a(n-2), n>2 ; a(0)=1, a(1)=4, a(2)=20 .

Terms

a(0) =1a(1) =4a(2) =20a(3) =104a(4) =540a(5) =2804a(6) =14560a(7) =75604a(8) =392580a(9) =2038504a(10) =10585100a(11) =54964004a(12) =285405120a(13) =1481989604a(14) =7695353140a(15) =39958755304a(16) =207489129660