2 Nov
2020
2 Nov
'20
1:54 p.m.
On Sun, 1 Nov 2020, 19:08 Keith F. Lynch wrote:
Dan Asimov wrote:
Or consider the number 73. Not particularly conducive to symmetry, you might think.
73 is a palindrome in Morse Code: --... ...--
This Morse code symmetry comes from the base-10 complement palindromic symmetry, n = reverse (c10 (n)) where c10 := d |-> 10 - d digit-wise (ill defined for d = 0). Similar complement-palindromes are 5, 19, 28, 37, ..., *73*, 82, 91,159, 258, ..., 1199, 1289, ... See oeis.org/A299539 (added in 2018). The Morse-palindromic numbers are exactly these plus those of odd length with the middle 5 replaced by a 0. - Maximilan