1,1

M. Gardner, Knotted Doughnuts and Other Mathematical Entertainments. Freeman, NY, 1986, p. 76.

G.f.: -2*x*(-6+5*x^2-4*x^3+x^4)/(1+x)/(x-1)^4.

Cf. A006071, A152132-A152134.

Sequence in context: A043140 A043920 A049598 this_sequence A080562 A033196 A060621

Adjacent sequences: A152132 A152133 A152134 this_sequence A152136 A152137 A152138

nonn,easy,more

R. J. Mathar, Mar 22 2009