Inverse Digit Sum (noch nicht übersetzt)
Problem 684
Define s(n) to be the smallest number that has a digit sum of n. For example s(10)=19.
Let S(k)=k∑n=1s(n). You are given S(20)=1074.
Further let fi be the Fibonacci sequence defined by f0=0,f1=1 and fi=fi−2+fi−1 for all i≥2.
Find 90∑i=2S(fi). Give your answer modulo 1000000007.