a(n) = binomial(2*n,n)*(2*n+1)/2+n*binomial(2*n-2,n)+(n-1)*binomial(2*n-2,n+1).

A344228

a(n) = binomial(2*n,n)*(2*n+1)/2+n*binomial(2*n-2,n)+(n-1)*binomial(2*n-2,n+1).

Terms

    a(0) =3a(1) =17a(2) =84a(3) =393a(4) =1778a(5) =7866a(6) =34254a(7) =147433a(8) =628914a(9) =2663934a(10) =11219728a(11) =47033322a(12) =196393044a(13) =817338580a(14) =3391858530a(15) =14040986985a(16) =57998364690a(17) =239112756630a(18) =984126777480

External references