A124817 Interpolation of A001764(n+1) and A006629(n).

1, 1, 3, 4, 12, 18, 55, 88, 273, 455, 1428, 2448, 7752, 13566, 43263, 76912, 246675, 444015, 1430715, 2601300, 8414640, 15426840, 50067108, 92431584, 300830572, 558685348, 1822766520, 3402497504, 11124755664, 20858916870, 68328754959

Offset: 0

Author

Paul Barry, Nov 08 2006

Keywords

• easy
• nonn

Comments

A column of number triangle A124816.

Formula

a(n)=(1/(2(n+3)))*C(3n/2+3,n/2+1)(1+(-1)^n)+(2/(n+3))*C(3(n+1)/2,(n-1)/2)(1-(-1)^n)