#math trivia for #September19: #262 is a palindrome that’s twice a palindrome. Which other day-numbers (1-365) have this property?
— Burt Kaliski Jr. (@modulomathy) September 20, 2013
We’re restricted to even palindromes, so our set of candidates (same forward and reverse) is:
- 2, 4, 6, 8
- 22, 44, 66, 88
- 202, 212, 222, 232, 242, 252, 262, 272, 282, 292
Among these, the only ones that are not twice a palindrome are 212, 232, 252, 272 and 292; the carry breaks the symmetry. The others are all twice a palindrome.
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