852017152

Appears in sequences

• a(0) = 0; for n >= 1, a(n) = 2^(n-1)*C(n-1), where C(n) = A000108(n) Catalan numbers, n>0.at n=13A052701
• Number of unrooted Eulerian maps with bicolored faces which are self-isomorphic under reversing the colors.at n=24A090375
• Number of walks within N^2 (the first quadrant of Z^2) starting at (0, 0), ending on the vertical axis and consisting of 2n steps taken from {(-1, -1), (-1, 0), (1, 1)}.at n=12A151374