A053750 Positions of 6's in the decimal expansion of Pi.

8, 21, 23, 42, 70, 73, 76, 83, 99, 109, 118, 119, 128, 182, 185, 201, 212, 213, 220, 227, 235, 240, 254, 258, 259, 264, 269, 277, 278, 287, 291, 310, 311, 313, 333, 348, 351, 360, 378, 379, 388, 398, 411, 427