A007976 Generalized Euler numbers O_n^+(2).

1, 2, 5, 16, 61, 275, 1430, 8506, 57205

Offset

1,2

Comments

"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]

References

A. A. Kirillov, Variations on the triangular theme, Amer. Math. Soc. Transl., (2), Vol. 169, 1995, pp. 43-73, see p. 52.

Links

Table of n, a(n) for n=1..9.

Marcelo Aguiar, Nantel Bergeron and Nathaniel Thiem, Hopf monoids from class functions on unitriangular matrices, arXiv preprint arXiv:1203.1572 [math.CO], 2012. - From N. J. A. Sloane, Sep 14 2012

A. A. Kirillov, On the combinatorics of coadjoint orbits, Funct. Anal. Applic., vol. 27 1992 pages 62-64.

Example

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

Crossrefs

Cf. A000111.

Sequence in context: A163747 A346838 A000111 * A058259 A361920 A368318

Adjacent sequences: A007973 A007974 A007975 * A007977 A007978 A007979

Keyword

nonn,more

Author

Alexandre Kirillov (kirillov(AT)math.upenn.edu)

Extensions

a(7) corrected by Dmitrii Pasechnik, Mar 27 2008

Status

approved