%I #28 Aug 03 2024 16:39:48
%S 1,2,5,16,61,275,1430,8506,57205
%N Generalized Euler numbers O_n^+(2).
%C "The numerical computations for small n in the simplest case q = 2 lead to the remarkable observations: the sequence {O_n^+(2)} is very close to the sequence ... of ... Euler numbers [A000111]." [Kirollov, 1995, page 52]
%D A. A. Kirillov, Variations on the triangular theme, Amer. Math. Soc. Transl., (2), Vol. 169, 1995, pp. 43-73, see p. 52.
%H Marcelo Aguiar, Nantel Bergeron and Nathaniel Thiem, <a href="http://arxiv.org/abs/1203.1572">Hopf monoids from class functions on unitriangular matrices</a>, arXiv preprint arXiv:1203.1572 [math.CO], 2012. - From _N. J. A. Sloane_, Sep 14 2012
%H A. A. Kirillov, <a href="http://dx.doi.org/10.1007/BF01768672">On the combinatorics of coadjoint orbits</a>, Funct. Anal. Applic., vol. 27 1992 pages 62-64.
%e a(7) is the number of conjugacy classes in a Borel subgroup of GL(7,2), also the number of complex irreducible representations and is easily computed by GAP to be 1430. - _Dmitrii Pasechnik_, Mar 27 2008
%Y Cf. A000111.
%K nonn,more
%O 1,2
%A Alexandre Kirillov (kirillov(AT)math.upenn.edu)
%E a(7) corrected by _Dmitrii Pasechnik_, Mar 27 2008