A171556 - OEIS

%I #7 Sep 30 2012 08:27:43

%S 1,1,4,13,40,124,394,1285,4288,14584,50386,176356,624034,2228698,

%T 8023318,29084533,106073008,388934368,1432916098,5301789568,

%U 19692361258,73398801058,274447690918,1029178840948,3869712441970,14585839204354

%N a(n)=3*C(n)-2, where C(n)=A000108(n).

%C Hankel transform is A171557.

%F G.f.: 3*(1-sqrt(1-4x))/(2x)-2/(1-x).

%F Starting with offset 1 = Narayana transform (A001263) of [1,3,3,3,...]. - Gary W. Adamson, Jul 29 2011

%F Conjecture: (n+1)*(n-2)*a(n) +(-5*n^2+11*n-4)*a(n-1) +2*(n-1)*(2*n-3)*a(n-2)=0. - _R. J. Mathar_, Sep 30 2012

%K easy,nonn

%O 0,3

%A _Paul Barry_, Dec 11 2009