x = 0xffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552bb9ed529077096966d670c354e4abc9804f1746c08ca237327ffffffffffffffff208552bb9ed529077096966d670c354e4abc9804f1746c08ca237327fffffffffffff

package main

import (
    "log"
    "math/big"
)

func main() {
    x := new(big.Int)
    y := new(big.Int)
    for size := 8; size < 64; size += 8 {
        bytes := make([]byte, size)
        for i := 0; i < size/2; i++ {
            bytes[i] = 0xFF
        }
        found := 0
        for loop := 0; ; {
            for i := size / 2; i < size; i++ {
                bytes[i] = byte(rand.Intn(256))
            }
            bytes[size-1] |= 1 // make it odd
            x.SetBytes(bytes)
            y.Exp(x, x, x)
            if y.BitLen() != 0 {
                if found == 0 {
                    log.Printf("#%d: %x => %x\n", loop, bytes, y)
                }
                found++
            }
            loop++
            if found > 0 && loop >= 1000 {
                log.Printf("size=%d found=%d/%d\n", size, found, loop)
                break
            }
            if loop >= 1<<20 {
                break
            }
        }
    }
}