ఏ సంఖ్య '?' స్థానంలో ఉంటుంది? 12, 23, 45, 89 ,?

Each term is double the previous one minus 1: 12 × 2 − 1 = 23, 23 × 2 − 1 = 45, 45 × 2 − 1 = 89, and 89 × 2 − 1 = 177.