239254

Appears in sequences

• G.f.: 1/(1-x) = Sum_{n>=0} a(n) * x^n / Product_{k=1..2*n} (1 + k*x).at n=6A208831
• Number T(n,k) of equivalence classes of ways of placing k 2 X 2 tiles in an n X 9 rectangle under all symmetry operations of the rectangle; irregular triangle T(n,k), n>=2, 0<=k<=4*floor(n/2), read by rows.at n=51A238581