What number would replace the question mark in the series: 1, 4, 11, 26, 57, 120, 247, ?

A424

B367

C255

D502 ✓ Correct

Correct answer: (D) 502

Explanation

The next term is 502.

Each term = 2 times the previous term plus a rising number.

1 x 2 + 2 = 4; 4 x 2 + 3 = 11; 11 x 2 + 4 = 26.

26 x 2 + 5 = 57; 57 x 2 + 6 = 120; 120 x 2 + 7 = 247.

247 x 2 + 8 = 502.

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