A026153 T(n,n-2), where T is the array in A026148.

1, 2, 7, 20, 60, 176, 517, 1512, 4415, 12870, 37477, 109044, 317109, 921870, 2679510, 7787904, 22636503, 65804638, 191332945, 556456060, 1618813834, 4710869108, 13713658368, 39935698400, 116340344575, 339050396646, 988474306017

Offset: 2

Author

Clark Kimberling

Keywords

• nonn

Crossrefs

First differences of A026327.

Formula

Conjecture: -(n+8)*(n-118)*a(n) +(-n^2-561*n-2878)*a(n-1) +2*(38*n^2+203*n-1070)*a(n-2) +2*(-116*n^2+781*n+2493)*a(n-3) +(13*n^2-1012*n+3888)*a(n-4) +3*(107*n-423)*(n-4)*a(n-5)=0. - R. J. Mathar, Jun 23 2013