1,2

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

R. L. E. Schwarzenberger, $N$-Dimensional Crystallography. Pitman, London, 1980, p. 34.

Bernd Souvignier, Enantiomorphism of crystallographic groups in higher dimensions with results in dimensions up to 6.

Sequence in context: A071897 A013923 A053466 this_sequence A054939 A081782 A081780

Adjacent sequences: A005028 A005029 A005030 this_sequence A005032 A005033 A005034

nonn

N. J. A. Sloane (njas(AT)research.att.com).

a(6) (found by Souvignier) sent by Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 16 2007