

A047072


Array T read by diagonals: T(h,k)=number of paths consisting of steps from (0,0) to (h,k) such that each step has length 1 directed up or right and no step touches the line y=x unless x=0 or x=h.


21



1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 1, 3, 2, 2, 3, 1, 1, 4, 5, 4, 5, 4, 1, 1, 5, 9, 5, 5, 9, 5, 1, 1, 6, 14, 14, 10, 14, 14, 6, 1, 1, 7, 20, 28, 14, 14, 28, 20, 7, 1, 1, 8, 27, 48, 42, 28, 42, 48, 27, 8, 1, 1, 9, 35, 75, 90, 42, 42, 90, 75, 35, 9, 1
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OFFSET

0,5


LINKS

Table of n, a(n) for n=0..77.
R. K. Guy, Catwalks, Sandsteps and Pascal Pyramids, J. Integer Seqs., Vol. 3 (2000), #00.1.6


EXAMPLE

Diagonals (beginning on row 0): {1}; {1,1}; {1,2,1}; {1,1,1,1}; {1,2,2,2,1}; ...


CROSSREFS

T(n, n)=A002420, T(n, n+1)=A000108 (Catalan numbers).
The following are all versions of (essentially) the same Catalan triangle: A009766, A030237, A033184, A059365, A099039, A106566, A130020, A047072.
Diagonals give A000108 A000245 A002057 A000344 A003517 A000588 A003518 A003519 A001392, ...
Sequence in context: A245618 A228053 A031262 * A178058 A260971 A053258
Adjacent sequences: A047069 A047070 A047071 * A047073 A047074 A047075


KEYWORD

nonn,tabl


AUTHOR

Clark Kimberling


STATUS

approved



