<br><font size=2 face="sans-serif">That's pretty neat! Perhaps I'll also
live to see the day when I understand symmetry breaking as it applies to
the early universe, which had no date! :-)</font>
<br>
<br><font size=2 face="sans-serif">Dave</font>
<br>
<br>
<br>
<br>
<br>
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<td width=40%><font size=1 face="sans-serif"><b>alexandre.wajnberg@skynet.be</b>
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<p><font size=1 face="sans-serif">05/10/2005 05:26 PM</font>
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<div align=right><font size=1 face="sans-serif">To</font></div>
<td><font size=1 face="sans-serif">SEQFANS <seqfan@ext.jussieu.fr>,
Eric ANGELINI <eric.angelini@kntv.be></font>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
<td><font size=1 face="sans-serif">Nicolas GRANER <nicolas.Graner@cri.u-psud.fr></font>
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<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">20th may, Historical date!</font></table>
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<br><font size=2><tt><br>
Hello dear Seqfans and friends,<br>
<br>
<br>
Nicolas Graner (member of the Oulipo litterary movement) has devised a
<br>
reflexion about symetric and palindromic caracters of some dates,<br>
which is urgent to transmit to us, mad of numbers.<br>
(and thanks to Éric Angelini for giving me this precious info!).<br>
<br>
20th february 2002 was very palindromic indeed:<br>
— 20022002 —<br>
<br>
And now approaches 20th may 2005,<br>
— 20052005 —<br>
a double-symetrical date.<br>
<br>
<br>
Explanation:<br>
1) Old electronic clocks and cheap calculator display<br>
the ten digits in squary figures comporting seven segments (think to <br>
the 8: seven segments).<br>
0, 1 and 8 have a vertical axis of symmetry; and 2 and 5 are mutually <br>
symmetric. From this, 25 four digit numbers may be constructed, having
<br>
a vertical axis of symmetry:<br>
<br>
0000 0110 0250 0520 0880<br>
1001 1111 1251 1521 1881<br>
2005 2115 2255 2525 2885<br>
5002 5112 5252 5522 5882<br>
8008 8118 8258 8528 8888<br>
(BTW they are a substring of A053701)<br>
<br>
So this year 2005 is the first symmetrical year since 124 years: 1881!<br>
And next one is 2115! (A rarity "Venus-transit" like)<br>
<br>
That's for the first half of "double-symmetrical date".<br>
<br>
<br>
2) If we consider the eight digits dates DDMMYYYY, there is, according
<br>
to Nicolas Graner, 98 such symmetrical dates.<br>
(the / are only for the lisibility and don't participate to the <br>
symmetry):<br>
<br>
10/10/0101 20/10/0105 01/10/0110 11/10/0111 21/10/0115 05/10/0120<br>
15/10/0121 25/10/0125 02/10/0150 12/10/0151 22/10/0155 08/10/0180<br>
18/10/0181 28/10/0185 10/01/1001 20/01/1005 01/01/1010 11/01/1011<br>
21/01/1015 05/01/1020 15/01/1021 25/01/1025 02/01/1050 12/01/1051<br>
22/01/1055 08/01/1080 18/01/1081 28/01/1085 10/11/1101 20/11/1105<br>
01/11/1110 11/11/1111 21/11/1115 05/11/1120 15/11/1121 25/11/1125<br>
02/11/1150 12/11/1151 22/11/1155 08/11/1180 18/11/1181 28/11/1185<br>
10/05/2001 20/05/2005 01/05/2010 11/05/2011 21/05/2015 05/05/2020<br>
15/05/2021 25/05/2025 02/05/2050 12/05/2051 22/05/2055 08/05/2080<br>
18/05/2081 28/05/2085 10/02/5001 20/02/5005 01/02/5010 11/02/5011<br>
21/02/5015 05/02/5020 15/02/5021 25/02/5025 02/02/5050 12/02/5051<br>
22/02/5055 08/02/5080 18/02/5081 28/02/5085 10/12/5101 20/12/5105<br>
01/12/5110 11/12/5111 21/12/5115 05/12/5120 15/12/5121 25/12/5125<br>
02/12/5150 12/12/5151 22/12/5155 08/12/5180 18/12/5181 28/12/5185<br>
10/08/8001 20/08/8005 01/08/8010 11/08/8011 21/08/8015 05/08/8020<br>
15/08/8021 25/08/8025 02/08/8050 12/08/8051 22/08/8055 08/08/8080<br>
18/08/8081 28/08/8085<br>
(Removing the 28 dates beginning with 0 and re-arranging the rest in<br>
increasing order gives another sequence we are submitting.)<br>
<br>
<br>
The 10/05/2001 was the first symmetrical eight digits date since eight
<br>
centuries!<br>
<br>
And now comes the point: if we take from this list the symmetrical <br>
dates both for the eight digits AND for the year, there is only four <br>
such dates:<br>
<br>
01/10/0110<br>
10/01/1001<br>
11/11/1111<br>
20/05/2005<br>
<br>
The first one doesn't count because of the beginning zero of the year;<br>
and the two next ones where ok but in the countries were time was ruled
<br>
by the christian calendar, the 0 was not in use! So the people were not
<br>
conscious of this feature of these two days.<br>
Conclusion :<br>
<br>
Friday the 20 may 2005<br>
— 20052005 —<br>
<br>
will be the only day in the whole<br>
past, present and future story of<br>
our calendar where human being will<br>
have the opportunity to be fully<br>
conscious to live a date presenting<br>
a vertical axis of symmetry both for<br>
its eight digits and for its two halves.<br>
<br>
<br>
<br>
How will the Seqfans and friends celebrate this historical and <br>
planetary event?<br>
<br>
Have a nice non-symmetrical day.<br>
<br>
Alexandre<br>
(but symmetrical year!)<br>
<br>
<br>
<br>
</tt></font>
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