OFFSET
0,3
COMMENTS
-a(n) is the Hankel transform of A127846, the series reversion of x/(1+5x+4x^2). Note that (4^n-1)/3 has g.f. x/(1-5x+4x^2).
MATHEMATICA
Table[4^Binomial[n, 2] (4^n-1)/3, {n, 0, 20}] (* Harvey P. Dale, Aug 29 2015 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Feb 02 2007
EXTENSIONS
More terms from Harvey P. Dale, Aug 29 2015
STATUS
approved