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So, if a is divisible by 3,

a+2 cannot be divisible as sum of digits cannot be divisible by 3 as 2 is not divisible by 3

a+4 cannot be divisible as sum of digits cannot be divisible by 3 as 4 is not divisible by 3

if a+2 is divisible by 3,

a cannot be divisible as sum of digits cannot be divisible by 3 as 2 is not divisible by 3

a+4 cannot be divisible as sum of digits cannot be divisible by 3 as 4 is not divisible by 3

if a+4 is divisible by 3,

a+2 cannot be divisible as sum of digits cannot be divisible by 3 as 2 is not divisible by 3

a cannot be divisible as sum of digits cannot be divisible by 3 as 4 is not divisible by 3