a(n) = Sum_{k=0..floor(n/4)} 2^k * 3^(n-3*k) * binomial(n-3*k+6,6) * binomial(2*(n-3*k),2*k).
A391724
a(n) = Sum_{k=0..floor(n/4)} 2^k * 3^(n-3*k) * binomial(n-3*k+6,6) * binomial(2*(n-3*k),2*k).
Terms
- a(0) =1a(1) =21a(2) =252a(3) =2268a(4) =17052a(5) =115290a(6) =741636a(7) =4705452a(8) =29807631a(9) =187564167a(10) =1160653536a(11) =7015318632a(12) =41344513938a(13) =237976030404
External references
- oeis: A391724