OFFSET
0,4
COMMENTS
Would appear to coincide with row sums of the inverse of the Riordan array (1-x^3,x(1-x^3)). These row sums have g.f. 1/(1-y-y^3+y^4) where y^4-y+x=0. - Paul Barry, May 10 2005
EXAMPLE
{1}, {2}, {3}, {4, 1}, {5, 2, 2}, {6, 3, 3, 3}, {7, 4, 1, 4, 1, 4, 1, 4, 1}
MATHEMATICA
Length/@Flatten/@NestList[ # /. k_Integer:>Range[k+1, 1, -3]&, {1}, 21]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wouter Meeussen, May 11 2003
STATUS
approved