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%I #6 Sep 29 2015 10:20:45
%S 3,5,7,7,7,11,13,13,13,17,19,19,19,23,23,23,23,23,29,31,31,31,31,31,
%T 37,37,37,41,43,43,43,47,47,47,47,47,53,53,53,53,53,59,61,61,61,61,61,
%U 67,67,67,71,73,73,73,73,73,79,79,79,83,83,83,83,83,89,89,89,89,89,89,89
%N Lower bound on a straddle prime pair.
%C Straddle primes that occur only once on either side of the composite number are lower and upper twin primes respectively.
%F Straddle primes are the nearest primes preceding and following a composite number n.
%e The first straddle prime pair is 3 and 5 which straddle the composite number 4.
%o (PARI) strad(n) = { my(y,pp,np); for(x=1,n, y=composite(x); pp=precprime(y); np=nextprime(y); print1(pp",") ) }
%K easy,nonn
%O 4,1
%A _Cino Hilliard_, Mar 13 2005
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