OFFSET
0,3
COMMENTS
Hankel transform of a(n) is 1,1,1,... (by construction). Hankel transform of a(n+1) is A145063.
Is this the same as the sequence s(n) that can be seen in Fig. 8 of Zhang (2015), with a different offset? - N. J. A. Sloane, Jan 28 2016
LINKS
Yan X Zhang, Four Variations on Graded Posets, arXiv preprint arXiv:1508.00318 [math.CO], 2015.
FORMULA
G.f.: 1/(1-x-x^2/(1-0x-x^2/(1-2x-x^2/(1-0x-x^2/(1-3x-x^2/...))))) (a continued fraction).
G.f.: 1/(U(0)+x^2) where U(k)= 1 - x*(k+1) - 2*x^2 - x^4/U(k+1) ; (continued fraction, 3rd kind, 3-step). - Sergei N. Gladkovskii, Oct 23 2012
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 30 2008
STATUS
approved