A046269 Largest prime substring in 3^n (0 if none).

0, 3, 0, 7, 0, 43, 29, 7, 61, 683, 9049, 71, 53, 59, 7829, 4348907, 3046721, 40163, 89, 62261467, 84401, 353203, 1381, 941, 2429536481, 288609443, 8329, 6255974849, 876792454961, 77364883, 113209, 3962839, 853020188851, 555523