a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(5*n-k,n-2*k).
A371787
a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(5*n-k,n-2*k).
Terms
- a(0) =1a(1) =5a(2) =44a(3) =441a(4) =4675a(5) =51129a(6) =570401a(7) =6451688a(8) =73715212a(9) =848793726a(10) =9833394285a(11) =114487194485
External references
- oeis: A371787