4,1
S. K. Lando and A. K. Zvonkin "Plane and projective meanders", Theoretical Computer Science Vol. 117, pp. 227-241, 1993.
P. Di Francesco, O. Golinelli and E. Guitter, Meanders: a direct enumeration approach, Nucl. Phys. B 482 [ FS ] (1996) 497-535.
4(2n)!/[3(n-4)!(n+6)! ] * (n^4+20n^3+107n^2-107n+15).
A diagonal of triangle A008828.
Sequence in context: A196671 A104901 A091962 * A200853 A159947 A030197
Adjacent sequences: A007743 A007744 A007745 * A007747 A007748 A007749
nonn,hard
Philippe Di Francesco (philippe(AT)amoco.saclay.cea.fr)
