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 A257749 Prime numbers that have a dodecagonal (12 sides) Voronoi cell in the Voronoi diagram of the Ulam prime spiral. 0
 61673, 635939, 706117, 720743, 1483439, 1742501, 1766701, 1847603, 2097959, 2163461, 2365289, 2429411, 3420101, 3490703, 3657361, 3920843, 3973829, 4758973, 4920887, 4989779, 5273753, 6167687, 6223247, 6573559, 6655409, 6694333, 6791881, 7095503, 7102349, 7338293, 7644541 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vardan Semerjyan, Voronoi diagram of prime spiral PROG (MATLAB) sz  = 3001; % Size of the N x N square matrix mat = spiral(sz); % MATLAB Function k = 1; for i =1:sz     for j=1:sz         if isprime(mat(i, j)) % Check if the number is prime             % saving indices of primes             y(k) = i; x(k) = j;             k = k+1;         end     end end xy = [x', y']; [v, c] = voronoin(xy); %  Returns Voronoi vertices V and % the Voronoi cells C k = 1; for i = 1:length(c)   szv = size(v(c{i}, 1));   polyN(i) = szv(1);   if polyN(i) == 12         A(k) = mat(y(i), x(i));         k = k+1;       end end % Print terms A = sort(A); fprintf('A = '); fprintf('%i, ', A); % When running the code be aware that the last terms you get might not be correct. % They correspond to the points on the outer edges of the spiral which might be % altered when considering a larger spiral. % Use larger spiral to get more terms CROSSREFS Cf. A257527, A257528, A000040. Sequence in context: A237013 A340438 A253613 * A340126 A112015 A234864 Adjacent sequences:  A257746 A257747 A257748 * A257750 A257751 A257752 KEYWORD nonn AUTHOR Vardan Semerjyan, May 07 2015 STATUS approved

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Last modified May 20 01:04 EDT 2022. Contains 353847 sequences. (Running on oeis4.)