a(n) = (27^n - 2^n)/25.A180844a(n) = (27^n - 2^n)/25.Terms a(0) =0a(1) =1a(2) =29a(3) =787a(4) =21257a(5) =573955a(6) =15496817a(7) =418414123a(8) =11297181449a(9) =305023899379External referencesoeis: A180844