a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(4*n-k,n-2*k).
A371786
a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(4*n-k,n-2*k).
Terms
- a(0) =1a(1) =4a(2) =27a(3) =209a(4) =1716a(5) =14553a(6) =125971a(7) =1105885a(8) =9809019a(9) =87691592a(10) =788832045a(11) =7131655908a(12) =64743390321a(13) =589808771881
External references
- oeis: A371786