grb=211, 223, 227, 229, 233, 239, 241, 251
grb=257, 263, 269, 271, 277, 281, 283, 293
n=3 to 100k done

the following prp were found

grb=211 n=41, 52301
grb=223 n=239, 241, 449, 13759
grb=227 n=5, 1061, 2687
grb=229 n=11, 29
grb=233 n=113, 9511, 17203
grb=239 n=5, 109, 2549
grb=241 n=17, 31, 80761, 92821
grb=251 n=7, 13, 17, 89, 227, 461, 3467, 57059
grb=257 n=23, 59, 487, 967, 5657
grb=263 n=5, 19
grb=269 n=none
grb=271 n=41, 79, 97, 313, 709, 829, 1213
grb=277 n=5, 19, 109, 1621, 90051
grb=281 n=none
grb=283 n=29, 31, 719, 12611
grb=293 n=3, 31, 6301, 7583

To be completed...