43584805013domain: NAppears in sequencesa(n) is the least prime of the form (3^j*5^k + 1)/2, j > 0, k > 0, j + k = n. a(n) = 0 if no such prime exists.at n=20A337425a(n) = 3*a(n-1) + 2*3^n - 1, a(0) = 0.at n=19A392084