a(n) = Sum_{k=1..n} binomial(2*k, k) * phi(k), where phi is the Euler totient function.
A356346
a(n) = Sum_{k=1..n} binomial(2*k, k) * phi(k), where phi is the Euler totient function.
Terms
- a(0) =2a(1) =8a(2) =48a(3) =188a(4) =1196a(5) =3044a(6) =23636a(7) =75116a(8) =366836a(9) =1105860a(10) =8160180a(11) =18976804a(12) =143784004a(13) =384483604a(14) =1625423764a(15) =6434066884a(16) =43771766404a(17) =98222578204a(18) =734437326604
External references
- oeis: A356346