A059221 Number of 3-bead necklaces where each bead is an unlabeled rooted tree, by total number of nodes.

1, 1, 2, 4, 8, 18, 43, 103, 255, 642, 1640, 4242, 11096, 29278, 77882, 208589, 562056, 1522606, 4144521, 11329608, 31090910, 85618848, 236530942, 655344579, 1820585313, 5070138554, 14151907583, 39584395796, 110938500821, 311481097178

Offset

0,3

Links

Table of n, a(n) for n=0..29.

Crossrefs

See A058855 (the 6-bead analog) for details.

Sequence in context: A318797 A318850 A052327 * A193617 A233139 A308246

Adjacent sequences: A059218 A059219 A059220 * A059222 A059223 A059224

Keyword

nonn

Author

N. J. A. Sloane, Jan 18 2001

Status

approved