doubleBasePalindromes(1000)应该返回1772。
testString: 'assert(doubleBasePalindromes(1000) == 1772, "doubleBasePalindromes(1000) should return 1772.");'
- text: doubleBasePalindromes(50000)应该返回105795。
testString: 'assert(doubleBasePalindromes(50000) == 105795, "doubleBasePalindromes(50000) should return 105795.");'
- text: doubleBasePalindromes(500000)应该返回286602。
testString: 'assert(doubleBasePalindromes(500000) == 286602, "doubleBasePalindromes(500000) should return 286602.");'
- text: doubleBasePalindromes(1000000)应该返回872187。
testString: 'assert(doubleBasePalindromes(1000000) == 872187, "doubleBasePalindromes(1000000) should return 872187.");'
```