a(n) = cosh(2*n*arcsinh(sqrt(n))).

A173174

a(n) = cosh(2*n*arcsinh(sqrt(n))).

Terms

    a(0) =1a(1) =3a(2) =49a(3) =1351a(4) =51841a(5) =2550251a(6) =153090001a(7) =10850138895a(8) =886731088897

External references