2 + 10 + 250 + 1250 = 1512
1512 + 1112 = 2624
103 + 2 = 105
105
756
This is an arithmetic progression with a first term of 1, a difference of 1, last term (and number of terms) 105. → sum = ½ × number_of_terms × (first_term + last_term) = ½ × 105 × (1 + 105) = ½ × 105 × 106 = 5565
105+105=210.
3341640 feet
756+756+756=1512+756=2268
1512 = 2 * 2 * 2 * 3 * 3 * 3 * 7 = 23 * 33 * 7
105 + 66 + 287 + 81 = 539
3024