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Greatest prime divisor of all composite numbers between n-th semiprime and next semiprime, or 1 if there are no such composite numbers.
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%I #11 Jul 11 2015 16:47:06

%S 1,2,1,3,1,5,1,3,1,7,1,1,3,1,11,3,5,13,7,1,5,7,17,7,19,13,7,1,1,11,23,

%T 1,1,17,11,19,29,1,5,1,1,31,13,1,23,1,1,3,1,37,13,1,5,41,7,43,1,13,23,

%U 31,47,13,1,1,17,1,23,53,1,1,3,1,1,11,37,29,59,61,31,7

%N Greatest prime divisor of all composite numbers between n-th semiprime and next semiprime, or 1 if there are no such composite numbers.

%C Largest of all prime factors of the numbers between semiprime(n) and semiprime(n+1). Semiprime analog of A052248. a(A070552(n)) = 1. This sequence defines a mapping of semiprimes to primes.

%F a(n) = MAX{(A001358(n) < k < A001358(n+1), A006530(k))}.

%Y Cf. A001358, A052248, A070552.

%K easy,nonn

%O 1,2

%A _Jonathan Vos Post_, Oct 24 2007

%E Corrected and extended by _R. J. Mathar_, Jan 15 2008