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%I #17 Jun 03 2019 11:49:29
%S 15,45,153,561,2145,8385,33153,131841,525825,2100225,8394753,33566721,
%T 134242305,536920065,2147581953,8590131201,34360131585,137439739905,
%U 549757386753,2199026401281,8796099313665,35184384671745
%N Number of lines in a Pauli graph of order n.
%C Apparently a duplicate of A028401. - _Michel Marcus_, May 28 2019
%C The number of vertices in a Pauli graph of order n is (4^n) - 1. Other invariants and a(n), are given in Table 5, p. 11, of Planat and Saniga.
%H Michel R. P. Planat and Metod Saniga, <a href="http://arXiv.org/abs/quant-ph/0703154">Pauli graph and finite projective lines/geometries</a>, arXiv:quant-ph/0703154, 2007.
%F Conjectures from _Colin Barker_, May 28 2019: (Start)
%F G.f.: 3*x^2*(5 - 20*x + 16*x^2) / ((1 - x)*(1 - 2*x)*(1 - 4*x)).
%F a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3) for n>4.
%F a(n) = (2 + 3*2^n + 4^n) / 2 for n>1.
%F (End)
%o (PARI) a(n) = my(t=2^(n-1), alfa=2^t-1, s=2*alfa); (t+1)*(s*t+alfa)/alfa; \\ _Michel Marcus_, May 28 2019
%Y Appears to be A028401.
%K nonn
%O 2,1
%A _Jonathan Vos Post_, Mar 21 2007
%E More terms from _Michel Marcus_, May 28 2019