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 Special feature (Posted on 2018-07-29)
What is the biggest even number N that can't be written as a sum of odd composite numbers?

Bonus: Find another feature unique to N.

 Submitted by Ady TZIDON No Rating Solution: (Hide) 38 Why? Consider the three odd composites 9,25,35. These are, respectively, 0,1,2(mod3). Thus, if n is an even number, one of n−9,n−25,n−35 is an odd composite divisible by 3 (well, supposing it is >3 at least). So 35+3=38 is the largest even number that qualifies! Some special features: 38 is the last Roman numeral when written lexicographically (XXXVIII). 38 is the largest known even number which can be represented as sum of two distinct primes in only one way: 38 = 31 + 7 38 is the sum of the squares of the first three primes: 38 = 2^2 + 3^2 + 5^2 38 is magic hexagon's smallest integer constant

 Subject Author Date No Subject Ady TZIDON 2018-08-06 21:08:58 re(3): computer solution and tidbits from a reference Dej Mar 2018-07-31 10:16:10 re(2): computer solution and tidbits from a reference Charlie 2018-07-30 12:21:41 re: computer solution and tidbits from a reference Dej Mar 2018-07-30 03:08:53 computer solution and tidbits from a reference Charlie 2018-07-29 13:06:40 Solution Jer 2018-07-29 11:13:33

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