A337423 a(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.
7, 37, 67, 337, 607, 3037, 15187, 27337, 49207, 683437, 0, 131835937, 659179687, 19929037, 35872267, 228881835937, 2491129687, 0, 0, 311391210937, 12013549804687, 0, 235357947067, 1176789735337, 0, 10591107618037, 52955538090187, 5675104819335937, 608185958862304687
Offset: 2