a(n) = Sum_{k=0..floor(n/3)} binomial(3*n-k+1,n-3*k).
A371774
a(n) = Sum_{k=0..floor(n/3)} binomial(3*n-k+1,n-3*k).
Terms
- a(0) =1a(1) =4a(2) =21a(3) =121a(4) =727a(5) =4473a(6) =27949a(7) =176549a(8) =1124332a(9) =7205511a(10) =46411744a(11) =300183757a(12) =1948255421a(13) =12681654613a(14) =82755728730a(15) =541213820732
External references
- oeis: A371774