a(n) = Pell(n)^3 + Pell(n+1)^3.

Terms

a(0) =1a(1) =9a(2) =133a(3) =1853a(4) =26117a(5) =367389a(6) =5169809a(7) =72744121a(8) =1023588937a(9) =14402985777a(10) =202665398173