It was proposed by Christian Goldbach that every odd composite number can be written as the sum of a prime and twice a square.

`9  = 7  + 2 * 1^2`  
`15 = 7  + 2 * 2^2`  
`21 = 3  + 2 * 3^2`  
`25 = 7  + 2 * 3^2`  
`27 = 19 + 2 * 2^2`  
`33 = 31 + 2 * 1^2`

It turns out that the conjecture was false.

What is the smallest odd composite that cannot be written as the sum of a prime and twice a square?