a(n) = 4*a(n-1) - 7*a(n-2) + 8*a(n-3) - 4*a(n-4) starting 0, 1, 4, 7.

Terms

a(0) =0a(1) =1a(2) =4a(3) =7a(4) =8a(5) =11a(6) =28a(7) =71a(8) =144a(9) =259a(10) =484a(11) =991a(12) =2072a(13) =4187a(14) =8236a(15) =16247a(16) =32544a(17) =65587a(18) =131572a(19) =262543a(20) =523688a(21) =1047179a(22) =2096956a(23) =4196903a(24) =8391600a(25) =16775011a(26) =33546244a(27) =67105087a(28) =134230328a(29) =268455611