OFFSET
1,1
COMMENTS
Number of generators of degree n of the Hopf algebra of 2-colored parking functions. Also, dimensions of the graded components of the primitive Lie algebra of the same Hopf algebra.
LINKS
J.-C. Novelli and J.-Y. Thibon, Free quasi-symmetric functions and descent algebras for wreath products and noncommutative multi-symmetric functions, arXiv:0806.3682 [math.CO], 2008.
FORMULA
a(n) = 2^n*A122708(n).
MAPLE
2^n*op(n, INVERTi([seq((k+1)^(k-1), k=1..n)]))
MATHEMATICA
terms = 16;
s = (1 - 1/(1 + Sum[(n+1)^(n-1)*t^n, {n, 1, terms}]))/t + O[t]^terms;
2^Range[16] * CoefficientList[s, t] (* Jean-François Alcover, Dec 14 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jean-Yves Thibon (jyt(AT)univ-mlv.fr), Jun 26 2008
STATUS
approved