A147719 A141479(n+1)/3.
1, 1, 1, 2, 6, 21, 91, 462, 2646, 16841, 117931, 900922, 7456086, 66453661, 634585771, 6463837382, 69955114326, 801626558481, 9696295037611, 123457062745842, 1650499351041366, 23116291464379301, 338474628835617451
Offset: 0
Keywords
Extensions
More terms from R. J. Mathar, Jan 22 2009