OFFSET
0,4
LINKS
R. Kehinde, S. O. Makanjuola and A. Umar, On the semigroup of order-decreasing partial isometries of a finite chain, arXiv:1101.2558.
FORMULA
T(n,0)= A000325(n-1) and T(n,k)=C(n,k), (k>0)
EXAMPLE
T (4,2) = 6 because there are exactly 6 order-preserving and order-decreasing partial isometries (on a 4-chain) of fix 2, namely: (1,2)-->(1,2); (2,3)-->(2,3); (3,4)-->(3,4); (1,3)-->(1,3); (2,4)-->(2,4); (1,4)-->(1,4) - the mappings are coordinate-wise
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Abdullahi Umar, Jan 12 2011
STATUS
approved