Problem 217Published on Friday, 14th November 2008, 09:00 pm; Solved by 991; Difficulty rating: 70%
A positive integer with k (decimal) digits is called balanced if its first ⌈k/2⌉ digits sum to the same value as its last ⌈k/2⌉ digits, where ⌈x⌉, pronounced ceiling of x, is the smallest integer ≥ x, thus ⌈π⌉ = 4 and ⌈5⌉ = 5.
So, for example, all palindromes are balanced, as is 13722.
Let T(n) be the sum of all balanced numbers less than 10n.
Thus: T(1) = 45, T(2) = 540 and T(5) = 334795890.
Find T(47) mod 315