A026572 a(n) = T(n,n-3), T given by A026568. Also a(n) = number of integer strings s(0),...,s(n) counted by T, such that s(n)=3.

1, 2, 8, 19, 56, 140, 376, 953, 2474, 6286, 16097, 40880, 104069, 264052, 670414, 1699831, 4310546, 10924970, 27690075, 70168812, 177820791, 450618964, 1142004584, 2894347667, 7336297080, 18597140982, 47148420564

Offset: 3

Author

Clark Kimberling

Keywords

• nonn

Comments

Also, a(n) = T(n,n-3), T given by A026584. Also a(n) = number of integer strings s(0),...,s(n) counted by T, such that s(n)=3.

Crossrefs

Cf. A026568, A026584.

Formula

Conjectured g.f.: (1/2)*((-3*x^2-x+1)*((x-1)/(4*x^2+x-1))^(1/2)-1+x+x^2)/x^3. - Mark van Hoeij, Oct 30 2011

Conjecture: (n+3)*a(n) +(-3*n-5)*a(n-1) +4*(-n-1)*a(n-2) +(13*n-9)*a(n-3) +(5*n-9)*a(n-4) +6*(-2*n+7)*a(n-5)=0. - R. J. Mathar, Jun 23 2013