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%I #7 Apr 26 2012 15:08:16
%S 0,0,0,1,2,1,0,5,4,7,0,5,0,0,2,0,0,13,0,0,10,0,0,0,22,0,20,25,0,7,0,0,
%T 10,0,32,5,0,35,20,0,0,25,0,0,22,0,0,5,0,47,46,0,0,35,0,0,40,0,0,1,0,
%U 0,10,0,0,35,0,0,0,0,0,25,0,0,14,0,0,5,0,77
%N Smallest k>0 such that n-k, n+k, 3n-k and 3n+k are all primes, or 0 if no such k exisis.
%e a(4)=1 because 4-1=3, 4+1=5, 3*4-1=11 and 3*4+1=13 are all primes,
%e a(5)=2 because 5-2=3, 5+2=7, 3*5-2=13 and 3*5+2=17 are all primes.
%t Table[k = 0; While[k < n && ! (PrimeQ[n - k] && PrimeQ[n + k] && PrimeQ[3 n - k] && PrimeQ[3 n + k]), k++]; If[k == n, 0, k], {n, 100}] (* _T. D. Noe_, Apr 26 2012 *)
%K nonn
%O 1,5
%A _Gerasimov Sergey_, Apr 26 2012