OFFSET
1,2
COMMENTS
Paths down an n-high rectangular-grid right triangle with interior neighbor fanout 2*2 + 1.
Column 2 of A180906.
Alternatively, this sequence corresponds to the number of nonnegative walks with n-1 steps {-2,-1,0,1,2} starting at the origin, ending at any altitude, and not going below the x-axis. - David Nguyen, Dec 01 2016
LINKS
R. H. Hardin, Table of n, a(n) for n=1..100
C. Banderier, C. Krattenthaler, A. Krinik, D. Kruchinin, V. Kruchinin, D. Nguyen, and M. Wallner, Explicit formulas for enumeration of lattice paths: basketball and the kernel method, arXiv:1609.06473 [math.CO], 2016.
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 23 2010
STATUS
approved