Search: id:A129336
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%I A129336
%S A129336 4,6,9,10,14,15,21,22,25,26,33,34,35,38,39,46,49,51,55,57,58,106,111,
%T A129336 115,118,119,121,122,123,129,133,134,141,142,143,145,146,155,158,159,
%U A129336 201,202,203,205,206,209,213,214,215,217,218,219,221,226,235,237,247
%N A129336 Digital clock semiprimes.
%C A129336 Semiprime analogue of A050246. Semiprimes possible on a 24-hour digital 
               clock, with no seconds. The largest value is 2359 = 7 * 337 because 
               23:59 is the largest 4-digit number that appears on a 24-hour digital 
               clock. On a 24-hour digital clock, there are 211 possible prime values: 
               how many semiprime values are there?
%H A129336 Randall Munroe, <a href="http://xkcd.com/c247.html">Factoring the Time</
               a>. The online comic xkcd.com has a digital clock factoring cartoon.
%H A129336 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               ClockPrime.html">Clock Prime.</a>
%e A129336 253 is in the sequence because (see the comic) a character looks at a 
               digital clock reading 2:53 and says: "253 is 11 x 23." That clock-time 
               is a semiprime.
%Y A129336 Cf. A001358, A050246, A118848, A118849, A118850.
%Y A129336 Sequence in context: A063762 A001358 A108764 this_sequence A103607 A108574 
               A157931
%Y A129336 Adjacent sequences: A129333 A129334 A129335 this_sequence A129337 A129338 
               A129339
%K A129336 base,easy,fini,nonn
%O A129336 1,1
%A A129336 Jonathan Vos Post (jvospost3(AT)gmail.com), May 27 2007

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