a(n) = Lucas(4n+1) - 1, or 5*Fibonacci(2n)*Fibonacci(2n+1).

A081017

a(n) = Lucas(4n+1) - 1, or 5*Fibonacci(2n)*Fibonacci(2n+1).

Terms

    a(0) =0a(1) =10a(2) =75a(3) =520a(4) =3570a(5) =24475a(6) =167760a(7) =1149850a(8) =7881195a(9) =54018520a(10) =370248450a(11) =2537720635a(12) =17393796000a(13) =119218851370a(14) =817138163595

External references