Search: id:A130827
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%I A130827
%S A130827 3,2,1,3,1,7,3,1,1,11,2,7,1,1,7,3,5,23,4,1,1,3,2,1,1,21,14,11,12,7,16,
               1,
%T A130827 1,1,26,37,1,1,4,21,6,31,4,25,1,71,14,1,10,1,10,371,36,1,3,1,1,185,2,43,
%U A130827 1,49,104,1,18,205,70,1,2,33,38,541,1,105,8,1,24,395,30,3,1,71,20,1,1,
               1
%N A130827 Least k >= 1 such that k^n+n is semiprime, or 0 if no such k exists.
%C A130827 k^n+n can be prime for not all n's (cf. A072883). What about semiprime 
               k^n+n? For which n's a(n)=0? Cf. A097792 (n such that x^n+n is reducible), 
               A072883 (Least k >= 1 such that k^n+n is prime, or 0 if no such k 
               exists).
%H A130827 Sean A. Irvine, <a href="b130827.txt">Table of n, a(n) for n=1,...,100</
               a>.
%e A130827 a(1)=3, a(2)=2 and a(3)=1 because
%e A130827 3^1+1=2^2+2=1^3+3=4=2*2 (semiprime),
%e A130827 a(4)=3 because 3^4+4=35=5*7 (semiprime), a(5)=1
%e A130827 because 1^5+1=6=2*3 (semiprime), a(6)=7 because
%e A130827 7^6+6=117655=5*23531 (semiprime).
%Y A130827 Cf. A072883, A097792.
%Y A130827 Sequence in context: A112745 A036585 A164848 this_sequence A070309 A130784 
               A119910
%Y A130827 Adjacent sequences: A130824 A130825 A130826 this_sequence A130828 A130829 
               A130830
%K A130827 nonn
%O A130827 1,1
%A A130827 Zak Seidov (zakseidov(AT)yahoo.com), Aug 18 2007
%E A130827 More terms from Sean A. Irvine (sairvin(AT)xtra.co.nz), Oct 20 2009

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