A132281

[zak seidov]

Dear Jonathan and others,

I suggest for consideration the next SEQUENCE.
I'd be happy if you'll contribute and co-submit it.
Thanks, Zak 


%I A000001
%S A000001
3,2,1,3,1,7,3,1,1,11,2,7,1,1,7,3,5,23,4,1,1,3,2,1,1,21,14,11,12,7,16,1,1,1,26,37,1,1,4,21,6,31,4
%N A000001 Least k >= 1 such that k^n+n is semiprime,
or 0 if no such k exists.
%C A000001 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).
%e A000001 a(1)=3, a(2)=2, and  a(3)=1 because
3^1+1=2^2+2=1^3+3=4=2*2 (semiprime),  
a(4)=3 because 3^4+4=35=5*7 (semiprime), a(5)=1
because 1^5+1=6=2*3 (semiprime), a(6)=7 because
7^6+6=117655=5*23531 (semiprime).
%Y A000001 A072883, A097792.
%O A000001 1
%K A000001 ,more,nonn,
%A A000001 Zak Seidov (zakseidov at yahoo.com), Aug 18
2007

--- Jonathan Post <jvospost3 at gmail.com> wrote:

>... And, Zak, you
> could give the near-cube semiprimes that correspond
> as by you and I,
> since we've gone so long without coauthoring....
> 
> -- Jonathan Vos Post


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