a(n) = a(n-1) + 16*a(n-3) - 16*a(n-4), where a(0) = 1, a(1) = 4, a(2) = 7, a(3) = 19.

Terms

a(0) =1a(1) =6a(2) =7a(3) =19a(4) =99a(5) =115a(6) =307a(7) =1587a(8) =1843a(9) =4915a(10) =25395a(11) =29491a(12) =78643a(13) =406323a(14) =471859a(15) =1258291a(16) =6501171a(17) =7549747a(18) =20132659a(19) =104018739a(20) =120795955a(21) =322122547a(22) =1664299827a(23) =1932735283a(24) =5153960755a(25) =26628797235a(26) =30923764531a(27) =82463372083a(28) =426060755763a(29) =494780232499