a(n) = 3^(n-2)*n*(5*n+1)/2.

Terms

a(0) =0a(1) =1a(2) =11a(3) =72a(4) =378a(5) =1755a(6) =7533a(7) =30618a(8) =119556a(9) =452709a(10) =1673055a(11) =6062364a(12) =21611934a(13) =75996063a(14) =264126177a(15) =908764110a(16) =3099363912a(17) =10489051017a(18) =35255264499a(19) =117775828656a(20) =391294693890