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%I #14 Dec 24 2014 01:08:36
%S 6,10,14,18,22,30,46
%N Coxeter numbers of the D-type Niemeier root systems.
%C These are exactly the even integers 2n such that the group Gamma_0(2n)+n has genus zero.
%H Miranda C. N. Cheng, John F. R. Duncan and Jeffrey A. Harvey, <a href="http://www.resmathsci.com/content/1/1/3">Umbral moonshine and the Niemeier lattices</a>, Research in the Mathematical Sciences, 2014, 1:3. See Eq. (23).
%F a(n) = 2*A133848(n+11). - _Omar E. Pol_, Dec 20 2014
%Y Cf. A091401.
%K nonn,fini,full
%O 1,1
%A _N. J. A. Sloane_, Jun 19 2014