a(n) = Sum_{k=0..n} binomial(n,k) * binomial(n+3*k,n-k).
A378404
a(n) = Sum_{k=0..n} binomial(n,k) * binomial(n+3*k,n-k).
Terms
- a(0) =1a(1) =2a(2) =12a(3) =74a(4) =464a(5) =2997a(6) =19704a(7) =131140a(8) =880912a(9) =5960000a(10) =40555117a(11) =277251834a(12) =1902791048a(13) =13101878220a(14) =90468268336a(15) =626202992439
External references
- oeis: A378404