A053747 Positions of 3's in the decimal expansion of Pi.

1, 10, 16, 18, 25, 26, 28, 44, 47, 65, 87, 92, 112, 116, 124, 138, 143, 171, 195, 197, 216, 217, 231, 232, 238, 262, 266, 275, 283, 284, 286, 301, 314, 347, 350, 359, 365, 366, 369, 383, 402, 403, 410, 421, 431