A027289 a(n) = Sum_{k=0..floor(n/2)-1} T(n,k) * T(n,k+2), with T given by A026009.

1, 3, 18, 55, 264, 847, 3744, 12465, 52868, 180895, 749220, 2617173, 10680656, 37915317, 153240864, 551019963, 2212417314, 8038946075, 32129224712, 117758845827, 469105048654, 1731917060158, 6882935960496, 25569740611270, 101442831429264, 378875492015643

Offset: 2

Author

Clark Kimberling

Keywords

• nonn

Extensions

More terms from Sean A. Irvine, Oct 26 2019