A050581 Numbers n such that 111*2^n-1 is prime.

2, 3, 6, 7, 21, 22, 23, 26, 29, 31, 58, 59, 67, 78, 83, 146, 159, 162, 165, 183, 262, 511, 718, 815, 1181, 1255, 1422, 1506, 1541, 1734, 2213, 3623, 4223, 4551, 5741, 5878, 6599, 11349, 12102, 17811, 19798, 20559, 26887, 32499, 40626, 43151, 49194, 52859, 98462, 101962, 126754, 133062, 147346, 217034, 279227, 345867, 362466, 378595, 448102, 520923, 602565, 656935, 791502