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S.o.d. classification (Posted on 2013-07-15) Difficulty: 4 of 5
There are 818,181 7-digit numbers divisible by 11, the smallest being 1,000,010 and the largest 9,999,990.
In each of them Sodd - Seven=0 mod 11, where Sodd represents the sum of the digits on odd numbered places in the number and Seven represents the sum of the digits on the even-numbered places.
for 1234563

Let's assign a number N to the set of all 7-digit numbers divisible by 11 in which
N=MAX(Sodd , Seven).
We shall call this set set #N , and denote by q(N) the number of its members.


EX1. q(1)=3, since there are 3 numbers possesing Sodd = Seven=1, namely:

EX2. Set #36 includes all the numbers having a pattern 9a9b9c9 (so that Sodd is 36 and a+b+c=3 mod 11); so q(36)=number of compositions of number 3 into 3 non-negative integers, triplets like 111,102....003,030,300 +number of compositions of number 14 into 3 non-negative integers, triplets like 059,068,,,167,158,149,...770,...950 +number of compositions of number 25 into 3 non-negative integers i.e. 799,889,898,979,988,997.

a. Which is the most numerous set?
b. List q(i) for 1=1 to 36.

(Inspired by KS's "Divisibility and Digit Sum",
revised and vetted by Charlie.)

No Solution Yet Submitted by Ady TZIDON    
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  Subject Author Date
Solutioncomputer solution (spoiler)Charlie2013-07-15 18:40:55
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