OFFSET
0,2
COMMENTS
Equals A000984, [1, 2, 6, 20, 70, ...] convolved with [1, 2, 0, 0, 0, ...]. - Gary W. Adamson, Jun 05 2009
FORMULA
a(n) = 2*A051960(n-1).
a(n) = 2*A000108(n)*(3n-1). - Ralf Stephan, Aug 24 2003
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved