Question

2 5 11 ? 23 complete series​

Answer 1

Answer:

The first few Thabit numbers are: 2, 5, 11, 23, 47, 95, 191, 383, 767, 1535, 3071, 6143, 12287, 24575, 49151, 98303, 196607, 393215, 786431, 1572863, ... (sequence A055010 in the OEIS)

First terms: 2, 5, 11, 23, 47, 191, 383, 6143, 786431

Largest known term: 3×211,895,718 − 1

Subsequence of: Thabit numbers