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H. Brown, R. Bülow, J. Neubüser, H. Wondratschek and H. Zassenhaus, Crystallographic Groups of Four-Dimensional Space. Wiley, NY, 1978, p. 52.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Table of n, a(n) for n=0..6.
W. Plesken and T. Schulz, Counting crystallographic groups in low dimensions, Experimental Mathematics, Volume 9 Issue 3 (2000), 321-478
Cf. A004027-A004031, A006226, A006227.
Sequence in context: A062940 A075813 A107952 * A123046 A237748 A087784
Adjacent sequences: A004029 A004030 A004031 * A004033 A004034 A004035
N. J. A. Sloane.
a(5)-a(6) from Henry Bottomley, Feb 03 2014