A034751 Dirichlet convolution of 3^(n-1) with itself.

1, 6, 18, 63, 162, 540, 1458, 4536, 13203, 39852, 118098, 356238, 1062882, 3193020, 9567396, 28711665, 86093442, 258324066, 774840978, 2324645406, 6973581924, 20921060700, 62762119218, 188287473024, 564859079523, 1694580407532