A026573 a(n)=T(n,n-4), T given by A026568. Also a(n) = number of integer strings s(0),...,s(n) counted by T, such that s(n)=4.

1, 3, 12, 34, 103, 281, 778, 2072, 5524, 14488, 37918, 98474, 255137, 658351, 1695542, 4356520, 11177720, 28637452, 73294698, 187412326, 478861373, 1222765699, 3120722598, 7961152560, 20302100415, 51757554237

Offset: 4

Author

Clark Kimberling

Keywords

• nonn

Formula

Conjecture: -2*(n-4)*(n+4)*a(n) +(5*n^2-5*n-46)*a(n-1) +(4*n^2+n+18)*a(n-2) +(-11*n^2+24*n-16)*a(n-3) +2*(n-2)*(2*n-5)*a(n-4)=0. - R. J. Mathar, Jun 23 2013