a(n) = (1/(3*n)) * Sum_{d|n} mu(n/d) * binomial(3*d,d).
A346577
a(n) = (1/(3*n)) * Sum_{d|n} mu(n/d) * binomial(3*d,d).
Terms
- a(0) =1a(1) =2a(2) =9a(3) =40a(4) =200a(5) =1026a(6) =5537a(7) =30624a(8) =173583a(9) =1001400a(10) =5864749a(11) =34768296a(12) =208267319a(13) =1258574114a(14) =7663720500a(15) =46976003712a(16) =289628805622
External references
- oeis: A346577