A027172 a(n) = (1/2) * A027170(2n, n).

5, 21, 78, 285, 1048, 3892, 14584, 55053, 209064, 797808, 3056870, 11752676, 45316898, 175175818, 678639148, 2634146413, 10241938408, 39882831448, 155519160718, 607181138848, 2373227900938, 9285480209458, 36364319046898

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

A027175(n) + 2.