OFFSET
0,6
FORMULA
G.f.=G=G(t, z) satisfies z^2*(2-4z+3z^2-t+2tz-3tz^2+t^2*z^2)G^2-(1-z)(1-2z+3z^2-2tz^2)G+(1-z)^2=0.
EXAMPLE
Triangle begins:
1;
1;
1,1;
1,3;
2,6,1;
6,10,5;
18,17,15,1;
Row n contains 1+floor(n/2) terms.
T(5,2)=5 counts (UD)(UHD), (UHD)(UD), H(UD)(UD), (UD)H(UD) and (UD)(UD)H, where U=(1,1), H=(1,0), D=(1,-1) (the low humps are shown between parentheses).
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Emeric Deutsch, Sep 02 2004
STATUS
approved