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A221310 Numbers m such that exactly four subsets of {m-1, m, m+1} sum up to a prime number.

%I A221310 #12 Jul 30 2019 19:50:06
%S A221310 1,2,3,6,30,660,810,2130,2550,3330,3390,5850,6270,10530,33180,41610,
%T A221310 44130,53550,55440,57330,63840,65100,70380,70980,72270,74100,74760,
%U A221310 78780,80670,81930,87540,93240,102300,115470,124770,133980,136950,156420,161460,168450
%N A221310 Numbers m such that exactly four subsets of {m-1, m, m+1} sum up to a prime number.
%C A221310 A117499(a(n)) = 4;
%C A221310 (a(n)-1,a(n)+1) are twin prime pairs for n >= 4.
%H A221310 Reinhard Zumkeller, <a href="/A221310/b221310.txt">Table of n, a(n) for n = 1..1000</a>
%e A221310 a(1) = 1: the required 4 subsets of {1-1,1,1+1} are: {2}, {0,2}, {1,2} and {0,1,2}.
%t A221310 Select[Range[170000],Count[Total/@Subsets[{#-1,#,#+1}],_?PrimeQ]==4&] (* _Harvey P. Dale_, Jul 30 2019 *)
%o A221310 (Haskell)
%o A221310 a221310 n = a221310_list !! (n-1)
%o A221310 a221310_list = map (+ 1) $ elemIndices 4 a117499_list
%Y A221310 Subsequence of A040040, apart from a(1)=1.
%K A221310 nonn
%O A221310 1,2
%A A221310 _Reinhard Zumkeller_, Jan 10 2013