OFFSET
0,2
LINKS
Robert Israel, Table of n, a(n) for n = 0..10000
S.-P. Eu, T.-S. Fu, Y.-J. Pan and C.-T. Ting, Baxter Permutations, Maj-balances, and Positive Braids, Electronic Journal of Combinatorics, 19(3) (2012), #P26. - From N. J. A. Sloane, Dec 25 2012
G. Nebe, E. M. Rains and N. J. A. Sloane, Self-Dual Codes and Invariant Theory, Springer, Berlin, 2006.
FORMULA
G.f.: u1/u2 where u1 := f(t^4) + t^156*f(t^-4), u2 := (1-t^4)^3*(1-t^8)^5*(1-t^12)^5*(1-t^20)^3 and
f(t) = 1 + 11*t^2 + 283*t^3 + 4055*t^4 + 37722*t^5 + 243578*t^6 + 1179852*t^7 + 4535052*t^8 + 14380814*t^9 + 38708195*t^10 + 90379766*t^11 + 186147868*t^12 + 342605290*t^13 + 569177435*t^14 + 860160090*t^15+ 1189401593*t^16+ 1511365669*t^17+ 1770220838*t^18+ 1914917488*t^19.
MAPLE
f:= unapply(1 + 11*t^2 + 283*t^3 + 4055*t^4 + 37722*t^5 + 243578*t^6 + 1179852*t^7 + 4535052*t^8 + 14380814*t^9 + 38708195*t^10 + 90379766*t^11 + 186147868*t^12 + 342605290*t^13 + 569177435*t^14 + 860160090*t^15+ 1189401593*t^16+ 1511365669*t^17+ 1770220838*t^18+ 1914917488*t^19, t):
u1:= f(t) + t^39*f(t^(-1)):
u2:= (1-t)^3*(1-t^2)^5*(1-t^3)^5*(1-t^5)^3:
S:= series(u1/u2, t, 51):
seq(coeff(S, t, j), j=0..50); # Robert Israel, May 02 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
G. Nebe (nebe(AT)math.rwth-aachen.de), Nov 10 2004
STATUS
approved