a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(3*n-2*k-3,n-2*k).
A390681
a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(3*n-2*k-3,n-2*k).
Terms
- a(0) =1a(1) =0a(2) =2a(3) =16a(4) =106a(5) =680a(6) =4344a(7) =27808a(8) =178634a(9) =1151664a(10) =7449842a(11) =48337216a(12) =314473688a(13) =2050800544a(14) =13402429520a(15) =87753566016a(16) =575547397450
External references
- oeis: A390681