a(n) = Sum_{k=0..n} (-1)^k * (3*k+1) * binomial(4*n-k+1,n-k)/(4*n-k+1).
A390500
a(n) = Sum_{k=0..n} (-1)^k * (3*k+1) * binomial(4*n-k+1,n-k)/(4*n-k+1).
Terms
- a(0) =1a(1) =0a(2) =1a(3) =6a(4) =40a(5) =284a(6) =2110a(7) =16210a(8) =127756a(9) =1027320a(10) =8395793a(11) =69534450a(12) =582337636a(13) =4923270360a(14) =41962170620a(15) =360182765930
External references
- oeis: A390500