%I A004027 M2060
%S A004027 1,2,13,73,710,6079,85311
%N A004027 Arithmetic n-dimensional crystal classes.
%D A004027 H. Brown, R. B\"{u}low, J. Neub\"{u}ser, H. Wondratschek and H. Zassenhaus, 
               Crystallographic Groups of Four-Dimensional Space. Wiley, NY, 1978, 
               p. 52.
%D A004027 P. Engel, ``Geometric crystallography,'' in P. M. Gruber and J. M. Wills, 
               editors, Handbook of Convex Geometry. North-Holland, Amsterdam, Vol. 
               B, pp. 989-1041.
%D A004027 W. Plesken and T. Schulz, Counting crystallographic groups in low dimensions, 
               Experimental Mathematics, 9 (No. 3, 2000), 407-411.
%D A004027 R. L. E. Schwarzenberger, N-Dimensional Crystallography. Pitman, London, 
               1980, p. 34.
%D A004027 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A004027 Experimental Mathematics, <a href="http://www.expmath.org/">Home Page</
               a>
%H A004027 W. Plesken and T. Schulz, <a href="http://wwwb.math.rwth-aachen.de/carat/
               ">CARAT Homepage</a>
%Y A004027 Sequence in context: A097349 A109112 A163190 this_sequence A154357 A161130 
               A007509
%Y A004027 Adjacent sequences: A004024 A004025 A004026 this_sequence A004028 A004029 
               A004030
%K A004027 nonn,hard,nice
%O A004027 0,2
%A A004027 N. J. A. Sloane (njas(AT)research.att.com).