a(n) = Sum_{k=0..floor(n/4)} binomial(n-k, 3k)*(-3)^(3k)*4^(n-4k).
A248089
a(n) = Sum_{k=0..floor(n/4)} binomial(n-k, 3k)*(-3)^(3k)*4^(n-4k).
Terms
- a(0) =1a(1) =4a(2) =16a(3) =64a(4) =229a(5) =592a(6) =-224a(7) =-18176a(8) =-175655a(9) =-1265732a(10) =-7914560a(11) =-44970752a(12) =-236014307a(13) =-1145932664a(14) =-5086940240a(15) =-19929220352a(16) =-61944816911a(17) =-81359219468a(18) =858917862064
External references
- oeis: A248089