a(n) = 7*a(n-1)-7*a(n-3)-a(n-4).

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =7a(5) =41a(6) =272a(7) =1853a(8) =12677a(9) =86794a(10) =594315a(11) =4069613a(12) =27867056a(13) =190822393a(14) =1306675145a(15) =8947587010a(16) =61269485263a(17) =419548848433