Answer:
115
Explanation:
1, 7, 13, 19, 25...
1, 1+6, 1+6+6, 1+6+6+6, 1+6+6+6+6...
In 2nd number, 1 plus one 6
In 3rd number, 1 plus two 6s
:
In 20th, 1 plus nineteen 6s
1 + 6 × 19 = 115
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