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%I #15 Jul 11 2015 16:51:00
%S 4,6,9,10,14,15,21,22,25,26,33,34,35,38,39,46,49,51,55,57,58,106,111,
%T 115,118,119,121,122,123,129,133,134,141,142,143,145,146,155,158,159,
%U 201,202,203,205,206,209,213,214,215,217,218,219,221,226,235,237,247
%N Digital clock semiprimes.
%C Semiprime analog of A050246. Semiprimes possible on a 24-hour digital clock, with no seconds. The largest value is a(414) = 2359 = 7 * 337 because 23:59 is the largest 4-digit number that appears on a 24-hour digital clock.
%H Nathaniel Johnston, <a href="/A129336/b129336.txt">Table of n, a(n) for n = 1..414</a> (full sequence)
%H Randall Munroe, <a href="http://xkcd.com/247/">Factoring the Time</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ClockPrime.html">Clock Prime</a>
%e 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.
%p with(numtheory): for h from 0 to 23 do for m from 0 to 59 do t:=100*h+m: if(bigomega(t)=2)then printf("%d, ",t): fi: od: od: # _Nathaniel Johnston_, May 17 2011
%Y Cf. A001358, A050246, A118848, A118849, A118850.
%K base,easy,fini,full,nonn
%O 1,1
%A _Jonathan Vos Post_, May 27 2007
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