%I #9 Mar 03 2023 09:33:04
%S 0,1,4,9,21,40,79,138,250,415,707,1126,1836,2837,4466,6723,10290,
%T 15167,22672,32805,48071,68470,98610,138491,196474,272559,381540,
%U 523417,724042,983415,1345848,1811341,2454994,3276807,4402076,5830801,7769950,10219523,13516934
%N a(n) = (A051894(n) - 1)/2.
%Y Cf. A051894.
%K nonn
%O 0,3
%A _N. J. A. Sloane_, Mar 02 2023