A027280 a(n) = Sum_{k=0..2n-3} T(n,k) * T(n,k+3), with T given by A026568.

26, 164, 1224, 7664, 51488, 326456, 2126376, 13574046, 87554326, 560845908, 3607790136, 23158545126, 148945375022, 957564479960, 6162874994108, 39672627184498, 255578754020002, 1647166273816172, 10622076015026288, 68529892093271816, 442357250742603624

Offset: 3

Author

Clark Kimberling

Keywords

• nonn

Extensions

More terms from Sean A. Irvine, Oct 26 2019