Determine the largest even positive integer that cannot be written as the sum of two odd composite positive integers.
38 is the answer
For an even integer over 38:
If it's 0 mod 3, then it equals 3*3+ an odd
multiple of 3;
If it's 1 mod 3, then it equals 5*5 + an
odd multiple of 3;
If it's 2 mod f 3, then
it's 35 plus an odd multiple of 3.
In all those cases there exist two composite addends.
Therefore the largest
possible one is 38.
In each of the above couples at least one number is a