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How many palindromes are there from one to six digits
One digit, nine
2-digit AA format, 9
3-digit ABA form, 9 * 10 = 90
4-digit Abba form, 9 * 10 = 90
5-digit abcba form, 9 * 10 * 10 = 900
6-digit abccba form. 9 * 10 * 10 = 900
To sum up, a total of (9 + 90 + 900) * 2 = 1998
One digit, nine
2-digit AA form, 9
3-digit ABA form, 9 * 10 = 90
4-digit Abba form, 9 * 10 = 90
5-digit abcba form, 9 * 10 * 10 = 900
6-digit abccba form. 9 * 10 * 10 = 900
To sum up, a total of (9 + 90 + 900) * 2 = 1998
[including 0, 1999]
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