Starting in the top left corner of a 2×2 grid, there are 6 routes (without backtracking) to the bottom right corner. How many routes are there through a 20×20 grid?2 × 2 のマス目の左上からスタートした場合、引き返しなしで右下にいくルートは …

The following iterative sequence is defined for the set of positive integers: n -> n/2 (n is even) n -> 3n + 1 (n is odd) Using the rule above and starting with 13, we generate the following sequence: 13 -> 40 -> 20 -> 10 -> 5 -> 16 -> 8 -…

Work out the first ten digits of the sum of the following one-hundred 50-digit numbers. 37107287533902102798797998220837590246510135740250 46376937677490009712648124896970078050417018260538 7432498619952474105947423330951305812372661730962…