a(n) = 4*a(n-1) + n with n > 1, a(1)=1.

Terms

a(0) =1a(1) =6a(2) =27a(3) =112a(4) =453a(5) =1818a(6) =7279a(7) =29124a(8) =116505a(9) =466030a(10) =1864131a(11) =7456536a(12) =29826157a(13) =119304642a(14) =477218583a(15) =1908874348a(16) =7635497409a(17) =30541989654a(18) =122167958635a(19) =488671834560