What will come in place of * in the sequence 3, 14, 39, 84, *, 258?

Examine differences: 14 − 3 = 11; 39 − 14 = 25; 84 − 39 = 45; next difference = ?; 258 − ? = ?. Check the pattern of differences: 11, 25, 45, ?, ?. Second differences: 25−11=14; 45−25=20; next: 20+6=26 (increment increases by 6 each time: 14, 20, 26, 32). So next first difference = 45 + 26 = 71. Then * = 84 + 71 = 155. Verify: next first difference = 71 + 32 = 103; then 155 + 103 = 258. ✓ Hence * = 155.